Noise levels (was VAX 11/780)

From: John Lawson <>
Date: Wed Dec 25 18:49:00 2002

On Wed, 25 Dec 2002 wrote:

> Umm, 90+ dB? Can this be right?? That seems awfully loud. Is that typical for
> larger machines?

 Direct measurement of my 11/44; 2 ESDI drives in an 11/23 chassis, 1
RL02: 79.1 dBC, _at_1 meter on-axis with front panel of CPU, quiet rural
house winter night ambient, B&K noise meter of known recent calibration.
Recorded spectra show strong peaks in the 300 - 600 Htz range, and quite a
bit of energy in the harmonics of the fan noise, going out to 8 - 10 kHtz.

  In the early 80s, a friend was an analyst for Quotron Systems (stock
trading and broker systems). I was several times in their big machine
room, which at the time had a hugish 11/782, several /750s and a couple of
/34s in some kind of data concentrator... many RP0x-type removable pack
drives, about a dozen TU-whatever tape drives, and the rest of the usual
suspects. The printer farm lived in it's own area, apart from the machine
room. With the HVAC going, and all the fans and motors, it was necessary
to shout to be heard, and (speaking as an audio professional) it was *at
least* 90dB all the time, probably more, based on my experience with
elevated noise environments.

> Just one more thing to take into account before I seriously consider moving any
> larger equipment in here . . .

  Like I said, it bugs me to distraction with this thing roaring away 5
feet behind me, and it's a decided relief when I shut 'er down and Peace
rules once again... ;}

  I *really do* want a "machine room" of some kind... even for my small
installation. My previous collection made even more noise, and *it* was
also in the damned room with me. Like I said: Someday......


Received on Wed Dec 25 2002 - 18:49:00 GMT

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