[time-nuts] time-nuts Digest, Vol 79, Issue 31

[shalimr9 at gmail.com]

In many instruments, a lot of the fan noise is actually noise from the air blowing over obstructions, so changing the fan will not reduce that noise, unless the air flow is reduced. That will be generally true for the type of equipment that dissipates a lot of heat in a small package, like a Tek 492/494 spectrum analyzer.
Support bars and perforated panels just in front of the fan are often not helping with the noise or the air flow. 
I think the 5370 is not that bad from an obstruction standpoint, and a lot of the noise is actually due to the age and design of the fan itself.
In some cases, mounting an AC fan on rubber mounts may help with vibrations, if you have the room.

I agree with Hal, in my experience, older AC fans with metal blades tend to be much noisier than recent DC fans with plastic blades for comparable air flow.

Didier KO4BB

Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: Hal Murray <hmurray at megapathdsl.net>
Sender: time-nuts-bounces at febo.com
Date: Thu, 10 Feb 2011 18:38:11 
To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
Reply-To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] time-nuts Digest, Vol 79, Issue 31


richard at karlquist.com said:
> I don't see why changing the operating voltage of the fan would make
> bearings last longer, move more air, or make less noise, unless it allows
> the fan to run at a different RPM.  Even then, more air and less noise would
> seem to be mutually exclusive. 

Somewhere in the past 10-20 years, people started paying much more attention 
to how much noise fans make.  For a given amount of air, most modern fans are 
a lot quieter than old ones.

I think one big step is to keep the support bars away from the fan blades and/or make them smaller.  There are probably some important details about the fan blade shape that I don't understand.


-- 
These are my opinions, not necessarily my employer's.  I hate spam.




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