When we have opened the case of the ASIC miner we’ve discovered that the cooling fan used inside is a 92mm Evercool EC9225M12CA, a mid range fan that does 2200 rpm with about 1.8W of power usage. Apparently the fan itself was sufficient to cool the miner with its 39.35 CFM of air flow and interestingly enough the specifications of the fan do say less than 25 dBA in terms of noise generated. The fan itself was directly soldered to the pins of the 6-pin PCI-E power connector on the unit, there is no thermal control or variable rpm, it is working at maximum all of the time. Running the miner without its metal casing has show us that it can be quite silent indeed, so the cause of the noise apparently was the metal case of the miner. More specifically the holes at the fan air intake that apparently are responsible for the significant increase of the noise level, so when TechnoBit has promised us a silent Bitcoin ASIC miner they should have modified the case of the device, so that it can really be silent and not the opposite – make a case that will increase the noise level way over what was promised in terms of specifications.