What does it really mean to have a 'silent PC'? Many companies these days advertise quiet computers, and some even bill theirs to be silent, but few vendors ever define what they actually mean by those terms.
Take this example from a review of a competitor of ours. Their marketing name for that computer includes the word silent, but based on the review it certainly was not inaudible - even at idle. A quote to drive this home, from the final page: "I have a hard time believing most users will be annoyed by the idle noise." The very fact they have to mention that implies there is enough noise present, even when the systems sits inactive, that it *might* bother some folks - yet they call the system 'silent'.
As a counterpoint, here is a link to the certification that Silent PC Review did on our latest version of the Serenity. They measured 11 decibels (dB) at idle, and less than 13dB under load from one meter away. At a normal sitting distance that means the computer they tested actually is silent, or very nearly so, to the human ear!
To be specific, the way we like to define these terms at Puget Systems is thus:
Quiet - From a seated position, most users will find the noise level pleasant and not annoying.
Often times a quiet computer's audible output will be eclipsed by any significant level of background noise, which can make it appear silent under some circumstances. Many of our computers - possibly even most - fall under this classification, and that level of low noise is all that many folks are looking for. Certainly anything in our Serenity line would at least qualify there, but the Serenity models which include SPCR certification have been tested to ensure they meet our standards of true silence.
Silent - From a seated position, most users will be unable to tell audibly whether the PC is on or off.
That is our gold standard, and we are deliberate to not imply silent computer operation where we do not meet this standard. Of course each person's hearing is a little different, but here at Puget Systems we take these terms very seriously. I've personally worked with folks who had specific frequencies of noise that bothered them, as is the case with medical conditions like hyperacusis and tinnitus, and we can almost always find a way to meet our customers' low-noise needs and build them a truly silent PC.
Our years of experience in this field really help, along with the things we've learned as a company from working with low-noise enthusiasts like the folks at Silent PC Review. We also have developed modification techniques, and continue to do so, to take existing hardware available on the market and improve on it in order to deliver solutions for our customers. I doubt we are the only company capable of such things, but because of the way in which some companies take liberties with terms like 'silent' I strongly recommend researching thoroughly before making any computer purchase.