The first (L-WAd) is the upper-limit A-weighted sound level, meaning it has been mathematically "weighted" to emphasize the 3-6 kilohertz range, where the human ear is most sensitive. It is usually measured in bels. The second (L-pAm) is the average A-weighted noise one meter away and is typically measured in decibels (one-tenth of a bel.) L-pAm can be excepted to be a little lower than L-WAd. (In the previous posting, the Dell figure was evidently equivalent to L-WAd, while the Fujitsu figure was not qualified.)
Using the L-pAm figure seems more appropriate in office settings. In that regard, the entry-level ProLiant ML110 Generation 5 had an L-pAm rating of 34 decibels while operating and 26 decibels while idleï¿¼for the SATA model. The SAS model was rated at 40 and 34 decibels, respectively. SAS drives spin at 16,000 rpm and the SATA drive spin at 7,500 rpm, and presumably that accounts for the difference.
All the ratings are less than 40 decibels, indicating that they should be endurable in a small office.
In future noise-related posting we'll look at noise ratings from other vendors of office servers.
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