Can CPUs Make PCs Faster & Quieter?

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Measuring And Rating Noise

Sound is commonly measured with a device called a sound level meter, or SLM. We rented a Norsonic SLM116 meter for this story, to make sure our sound measurements were as accurate as possible. Sound is measured in decibels (abbreviated dB), and is based on an equation called A-weighting that compensates for differences between the way the human ear hears sounds and the way that electronics detect them. That's why the measure of sound pressure most commonly used is written dBA, to indicate that the reading has been corrected to match human hearing as much as possible (humans perceive low and high frequencies much less acutely than mid-range ones, whereas good electronics should be equally sensitive throughout the entire audible spectrum, usually from 20 Hz to 20,000 Hz; thus, A weighting reflects non-linear human hearing).

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dBABrief descriptionRemarks
0Human hearing thresholdInaudible at any distance
<15Human body soundsNormally inaudible(breathing, heartbeat, digestion, etc.)
15-20Super, quiet fanless PCBarely audible
20-25Quiet whisper, barely audible PCVery quiet(ambient sound level in recording studio)
25-30Bedroom at night, very quiet PCQuiet
30-45Quiet office or library, typical PCSomewhat audible
50Conversation at 1m, noisy PCClearly audible
60Restaurant or mall, noisiest PCNoisy
80Curbside on busy streetVery noisy
100Machine shop, printing pressExtremely noisy
120Boiler room, ship engine roomNearly intolerable
14030m from jet engine at takeoffThreshold of pain

Table 1: Sound levels as humans perceive themSource: "What is Sound? And Noise?" by Mike Chin, www.silentpcreview.com; reproduced by permission.

The background noise level we measured in a tightly-sealed closet set the baseline for our numbers at 31.7 dBA. According to the preceding scale, we were only able to achieve sound levels at the lower end of the typical PC range. As a useful point of comparison, we also measured sound output from a desktop PC that one of our writers assiduously tweaked to reduce noise output. We were able to beat those numbers in all cases but one. This PC produced sound levels between 39.0 dBA and 42.0 dBA. We'll also do our best to characterize the noise that the two builds emitted, such as it was.