Zalman CNPS 9900 DF review

Noise Levels

With a certified dBA meter we measure how many dBAs originate from the PC. It's slightly subjective as there is always noise in the background, from the streets, from the HD, PSU fan, etc so this is by a mile or two not a precise measurement. You could only achieve objective measurement in a sound test chamber. Take this measurement as an indication, not a precise measurement please.

The human hearing system has different sensitivities at different frequencies. This means that the perception of noise is not at all equal at every frequency. Noise with significant measured levels (in dB) at high or low frequencies will not be as annoying as it would be when its energy is concentrated in the middle frequencies. In other words, the measured noise levels in dB will not reflect the actual human perception of the loudness of the noise. That's why we measure the dBA level. A specific circuit is added to the sound level meter to correct its reading in regard to this concept. This reading is the noise level in dBA. The letter A is added to indicate the correction that was made in the measurement. Frequencies below 1kHz and above 6kHz are attenuated, whereas frequencies between 1kHz and 6kHz are amplified by the A weighting.

But let's have a peek at noise levels. We take a dBA gun and point it at the working PC and take a distance of 75 CM. The PC again is stressed at 3200 MHz on the CPU with 80% RPM set in the BIOS. These, as such, are noise levels measured under heavy CPU load. Above we see in IDLE a noise level of 40 BDa, that's definitely a little on the high side.

The CNPS 9900 DF shows a 42 DBa noise level. That means you can hear the cooler. If you prefer silence then use a resistor wire or fan controller and easily shave off another 2 DBa.

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