Noise levels - Sound pressure readings
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 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.
|TYPICAL SOUND LEVELS|
|Jet takeoff (200 feet)||120 dBA|
|Construction Site||110 dBA||Intolerable|
|Shout (5 feet)||100 dBA|
|Heavy truck (50 feet)||90 dBA||Very noisy|
|Urban street||80 dBA|
|Automobile interior||70 dBA||Noisy|
|Normal conversation (3 feet)||60 dBA|
|Office, classroom||50 dBA||Moderate|
|Living room||40 dBA|
|Bedroom at night||30 dBA||Quiet|
|Broadcast studio||20 dBA|
|Rustling leaves||10 dBA||Barely audible|
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 3300 MHz on the CPU with 80% RPM set in the BIOS. These, as such, are noise levels measured under heavy CPU load:
On average and with a PWM regulated controller, the noise level could be lower. The cooler with fan is hardly audible and remains under the overall system noise, that just really really good.
Of course passively the cooler does not make any sound so I gave it a 1 dBA value just for the sake of the chart.