Noise abatement for a rack

Joel Jaeggli joelja at
Wed Dec 4 12:01:28 PST 2002

our chatsworth megaframe cabinets are fairly quiet relative to open racks
but require directed ac, blown in under the floor and exhausted out the

This also has the effect of isolating the enviroment in the cabinets from 
the rest of the room somewhat, which is desireable when you have a pair of 
half rack sized routers drawing 1.5kw each in one cabinet.

I would except that most reasonable acoustic materials are likely to cause 
your airflow requirements to go up given that you'll be blocking most of 
surface area that is currently radiating heat with something that's also 
thermal insulation and that you aren't currently blowing air into 
something that's an open rack. your temperature monitoring requierments 
will also go up since likelyhood of hardware failure goes way up if the 
airflow stops.


On Wed, 4 Dec 2002, David Mathog wrote:

> Anybody here ever try noise insulating a rack???
> I have to share a room with our new 20 node cluster
> and it would be nice to be able to do so without having
> to wear earplugs all the time.  The 20 2U single Athlon
> systems are mounted in an open frame 4 post rack.  Using a 
> Radio Shack sound level meter (catalog #33-2055) set to
> dBA, fast weighting the following values were obtained
> for (front,left side, back, right side):
> room ambient (no power) <50dBA  (below detection limit)
> 1  node  at 6"  from side, front panel open:    66,59,67,63
> 1  node  at 6"  from side, front panel closed:  63,58,67,62
> 1  node  at 48" from side, f.p. closed:         53,- ,- ,55
> 20 nodes at 6"  from side, f.p. closed:         72,70,76,72
> 20 nodes at 48" from side, f.p. closed:         66,- ,- ,66
> As you'd expect - it's all fan noise.  The left side
> is quieter than the right because there are fewer ventilation
> holes on that side and the dual internal fans are mounted
> closer to the right side of the case.  My goal is to drop
> the dBA at 48" down to no more than 53 dBA with all nodes
> operating.
> Sound measurements next to an Antec SX-630 case (no
> sound insulation, just sheet metal) were 65 dBA with
> the side off, 57 with the side on.  So adding sides to
> the open rack may help a little and shouldn't be much
> of a problem for ventilation.  But how to treat the front
> and back of the case???  If I close them off with a 
> solid sheet of sound absorbing material (lead would work
> but something a bit less expensive and toxic
> would be better) the system will become really quiet
> - because it's going to overheat and die.  Some sort of
> sound absorbant coated louvers maybe?  Or for the back,
> since it's close to a wall, coat the wall with sound
> absorbing tile?
> Hopefully somebody has already dealt with this.  But
> if the solution is out there on the web I've not found it.
> All the racks I saw were just sheet metal and the front/back
> doors, if any, were either plastic or metal grillwork - good
> for maybe a 3-4 dBA sound reduction.
> Regards,
> David Mathog
> mathog at
> Manager, Sequence Analysis Facility, Biology Division, Caltech
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Joel Jaeggli	      Academic User Services   joelja at    
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