Tested: Noise level of our 1U Rack Computers

Posted by Geoff Undrell on: in: Development Projects, Products

As our new look 1U Rack Computers enter production we have taken some time to test our new Active Fan Controller. We have been developing the system fan controller module  in response to customer feedback asking for quieter Rack mounted computers over the last few months.

Audio testing at the lower end of the spectrum, >35dB, is quite difficult because a lot of sound measurement devices are designed for testing the higher health & safety limit. However, a EMC/LVD test house kindly lent us their anechoic chamber which although normally used for electromagnetic testing, had an ambient noise less the 24dB.

The test procedure was performed in accordance with Directive EN ISO 3746:2009, using a calibrated Casella CEL-240 Sound Level Meter mounted 1 meter from the rear of computer and connected via USB to a laptop which recorded the results.

We tested three different Rack Computer specifications in the aim to demonstrate to our customers the affect CPU performance can have on heat build up in the case and thus noise created by cooling. In each test the CPU was loaded to approximately 40%  for 1 hour using an application that creates artificial load.

Test Results

1U Rack PC C12 using Intel Atom CPU and only requires one 40mm cooling fan and measured 34dB.

1U Rack PC C34Z using an Intel I3-4130 CPU had three 40mm cooling fans and measured 42dB.

1U Rack PC C74z using an Intel i7-4770 CPU had three 40mm cooling fans and measured 46.5dB.

The first thing to understand from the results is that the Decibel Scale in not linear, for example the perceived difference between 30dB and 40dB is actually twice as loud. The Decibel Scale is very complex, so for the purpose of this test I wanted to give you some examples to compare it to in everyday life:

Whisper Quiet Library or Bedroom at night – 30dB

Normal library noise or a running stream – 40dB

Normal Conversation or a quiet office – 60dB

Conclusion

I think it is clear to say that our Intel Atom C12 rack computer is VERY quiet and rightly so because it has a fanless CPU and only has two cooling fans (one in the power supply). So if you need an entry level quiet PC for a low performance application then this is the unit to go for.

The comparison between the C34z and C74z is then an interesting one because you need to bear in mind that both CPUs were loaded to 40%. This means that the i7 was in fact performing more functions than the i3 and so the relative difference between the two is not so far apart.