Here's where we arrive at actually testing the Silentium. We'll do this in two stages. First we'll simply hotwire the chassis so that all fans activate themselves and start spinning. This will give us a rough idea of how loud or silent the actual chassis itself is.

Now mind you, we test with an open system. You obviously would have it closed, which is even more silent.

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, where as frequencies between 1kHz and 6kHz are amplified by the A weighting. 

We measure with a DBa meter. Our offices however are stationed in a city. During daytime in a silent room though on average would still create a virtually silent, yet noise level at ~29 DBa.

Now as you can see ... we activated the PSU here and the fans started spinning. Immediately you'll notice that the fans are tediously silent as we managed to get a 31.6 DBa sound pressure.  But let's throw in a HDD and motherboard.

Now here's what I did. To make sure our components did not influence the results we took, I installed a passive motherboard with integrated GPU (GF9300). I then put in a Intel Core 2 Quad processor (stock clocks) with a passive cooler. The I added a WD 1 TB Green drive into the HDD muffler. We booted into windows Vista and then measured again.

Check that out ..  32.4 DBa with the side panel open. That's amazing. Obviously when we'd use an active fan on the CPU or a high-end graphics card, that number would change. But since we are testing a silent chassis here, this seemed to me the proper way to measure.

Now here's a thought .. if you absolutely hate noise .. this would be a perfect working PC. If you take it up a notch and build the PC like this (passive) it would make a incredible nice HTPC as well. So there's a good number of application I think of for the Silentium. Also a small side note, with the panel closed, we noticed pretty normal airflow, meaning heat was transported out of the chassis very well.

32 DBa ... amazing. No noise, no resonating stuff. This is pretty interesting.