Another one to check out before it goes live...


'''Fan noise''' can be a persistant minor irritant. The good news is
that [[:Category:Noise|noise reduction]] is fairly simple to install,
and can reduce noise levels massively.


===Buying quiet===
Extractor fans cover the noise level range from under 40dB to over
50dB. Choosing a low noise fan at purchase time can reduce noise by
upto 10dB.

===Flexible mounting===
Fans can be mounted on rubber washers (or other flexible mounts) to
prevent transmission of vibration to the wall or joist.

To be effective, screws should be done up until there is no slack
movement, but no further. Overtightening would eliminate the
flexibility of the mounting.

       ___
      |_ _|     <--- screw head
     === ===    <--- penny washer
     === ===    <--- tap washer
  ====== ====== <--- fan case
     === ===    <--- tap washer
  ////// ////// <--- wall
  ////// //////

 Simple but effective flexible mounting

For large fans mounted by threaded steel rod, the rod can sit in a
wider hole lined with soft plastic pipe, with rubber washers top and
bottom to allow a tiny bit of movement.


           __||__           <--- threaded rod protruding
          |      |          <--- locking nut
          |______|
          |      |          <--- locking nut
          |______|
        ____________        <--- penny washer
        ____________
 ______|__        __|______ <--- rubber tap washer
          | |  | |
          | |  | |
          | |  |<----- threaded rod
          | |  | |
          | |  | |<--- soft plastic pipe
          | |  | |
  Joist   | |  | |     Joist
          | |  | |
 _________| |  | |___________
       |____________|      <--- tap washer
        ____________       <--- penny washer
          |      |
          |______|         <--- locking nut
             ||
             ||            <--- threaded rod
             ||

Various sizes of soft (rubbery) plastic pipe can be had from car
accessory dealers etc.


===Damping===
Attaching damping material to the fan case interior can
[[:Category:Noise|reduce noise]] to some degree. Of course the damping
material should not get close to the fan blades, nor block [[Motor
repair|motor]] cooling airflow. A fireproof or self extinguishing
material is to be recommended, as fans do catch fire at times.

The amount of [[:Category:Noise|noise reduction]] this provides is
limited, but its very simple to do, and nothing is visible when the
work is finished.


===Speed control===
Reducing fan speed at times when full extraction isn't needed reduces
noise a fair bit. It does also heavily reduce flow rate, but in some
cases this is acceptable.

Permanent speed reduction can achieve quite a bit of [[:Category:Noise|
noise reduction]] with some fans. This is most simply done with a
[[Droppers|dropper]] or transformer for small amounts of reduction, or
an electronic controller for larger amounts.

In the few cases where motor noise is a large component of total
noise, reducing speed is not very effective. However these fans are in
the minority.

===Remote mounting (eg attic)===
Remote mounting of fans reduces noise transmission to the house
interior. This is often done with bathroom extractor fans, an inline
fan is mounted in the loft.

===Bigger fan===
A bigger fan running slower produces less noise when all other things
are equal. Naturally all other things are rarely equal, but looking at
fans a size up run at reduced speed can often get you a lower noise
figure.

The downside is that purchase price goes up rapidly as fan size
increases.

===Balancing & levelling blades===
With ceiling fans, balancing and levelling the blades can make quite a
difference.

This sometimes helps with other types of fan if the metal blades have
become bent out of alignment - though some seem to work quite happily
with blades pointing all over the place.

Blade alignment and balance primarily addresses shaking, thumping,
flapping and other low frequency noises. It does also have some effect
on the high frequency air movement noise, but not as much.


===Duct choice===
Corrugated flexible ducting has considerable resistance to airflow,
necessitating the use of a more powerful fan to get sufficient flow.
Rigid duct enables use of a quieter fan.


===[[Baffle box]]===
A well baffled air path can produce major [[:Category:Noise|noise
reduction]]. This measure can produce much more result than the
others, and is used for serious noise problems. It can be used not
only to reduce fan & motor noise, but also to filter out almost all
the noise from outdoors when moving air in or out.

When installing a remote fan in the attic, this effect can be
incorporated to a limited but still useful extent simply by snaking
the air tube. This is not nearly as effective as a proper [[baffle
box]], but its relatively easy to do.

===Single baffle===
The diminutive form of the baffle box is an empty box lined with
[[carpet]] (or other material) with an outlet hole at 90 degrees to
the inlet. These give modest noise reduction, but are very easy and
quick to construct. Small boxes for computer fans can even be made
from [[Damping material|triplewall cardboard]].

These are mainly used to quieten portable appliances such as
computers, projectors, lab equipment etc.


==See Also==
* [[:Category:Noise]]
* [[Special:Allpages|Wiki Contents]]
* [[Special:Categories|Wiki Subject Categories]]



[[Category:Noise]]
[[Category:Cooling]]
[[Category:Bathrooms]]
[[Category:Kitchens]]


NT

wrote in message 
news:e8fdb6bc-2f87-47ee-95fc-6e29473051bd@k7g2000hsd.googlegroups.com...
> Another one to check out before it goes live...
>
>
> '''Fan noise''' can be a persistant minor irritant. The good news is
> that [[:Category:Noise|noise reduction]] is fairly simple to install,
> and can reduce noise levels massively.
<snipped>

Or better still get this firm to manufacture a 240Volt model external fan 
for the British market.
See,   http://www.continentalfan.com/ext.htm

Don