Noise dampening

[Watson A.Name - \"Watt Su]

"N. Thornton" <bigcat@meeow.co.uk> wrote in message
news:a7076635.0410111344.51e2f64c@posting.google.com...

"James Varga" <james@jamesvarga.com> wrote in message
news:<10mjaef1nkb408f@corp.supernews.com>...
To dampen something is to make that something moist.

The word you are looking for is damping.

I'm sure everyone knew what I meant

Thanks everyone for your help - I'll see what I can come up with.

I think a mechanical screen outside the house would give more result.
Also sitffening up the house structure and ading damping materials
wherever poss, eg fibreglass under floorboards, within wood frame
walls, etc. FG not only damps noise transmission, but it also damps
panel resonance, which is a big contributor to noise transmission.

We have an office right next to, and shares a wall with an electrical
room. The occupant complained about the constant hummm from the
transformer. The maintenance dept put 3 or 4" fiberglass batting all
over the wall in the electrical room, to damp the noise. Well, as you
might imagine, it didn't help at all. The reason is that the fiberglass
will absorb higher freqs with wavelengths that get lost in its labyrinth
of fibers, but it has very little mass so any low freq wave just moves
it and the wall like a diaphragm, allowing the sound to go right thru.

The moral is, if you want real low freq soundproofing, put up a wall of
corrugated steel on a steel frame and spray a couple inches of gunite
cement on it to make it even stiffer and add mass to it so that its
resonant freq is below the audible range. Or if you're in an area
that's not prone to earthquakes, then put up a brick wall or cinder
block wall.

Wood structures can be stiffened by adding more wood to make it
thicker/wider, bracing, or attaching steel to the sides of wood
members.

That's exactly the *wrong* thing to do! Stiffening the structure raises
its resonant freq, and the structure turns into a drumhead! You want to
LOWER the resonant freq, so adding mass is necessary.

Also, or better, look up how the BBC produce panels for noise
stopping, ISTR them called Camden or something similar, basicaly they
found out how to make very noise proof panels based on plasterboard.

The fact that its 300 yo of course complicates this a fair bit, as you
wont want to PB line your limed walls, fill in beamed ceilings etc.

Ventilation is quite easy: use a hole in the wall fan with the airflow
fed into a maze-like box with all the maze lined with ordinary carpet.
Very effective. Use a fan designed for use with ducting so it has
enough pressure head.

Finally, is there enough distance to plant a thick hedge? That would
surely help, though you'd want a real high hedge if poss.


NT

 

[Rich Grise]

On Monday 11 October 2004 06:41 pm, Watson A.Name - "Watt Sun, the Dark
Remover" did deign to grace us with the following:

"N. Thornton" <bigcat@meeow.co.uk> wrote in message
news:a7076635.0410111344.51e2f64c@posting.google.com...

Wood structures can be stiffened by adding more wood to make it
thicker/wider, bracing, or attaching steel to the sides of wood
members.

That's exactly the *wrong* thing to do! Stiffening the structure raises
its resonant freq, and the structure turns into a drumhead! You want to
LOWER the resonant freq, so adding mass is necessary.

So, stucco on the wall facing the road would help, no?

Thanks,
Rich

 

[Phil Allison]

"N. Thornton"

Adding mass without stiffness is very inefficient.

** The most effective *soundproofing* material you can get is lead sheet
added all over a plaster or timber wall. Lead sheet adds huge mass and a
little damping.

Otherwise, replace the offending wall with a nice brick one - has huge
mass and stiffness.




............. Phil

 

[Spehro Pefhany]

On Tue, 12 Oct 2004 23:13:34 +1000, the renowned "Phil Allison"
<philallison@tpg.com.au> wrote:

"N. Thornton"


Adding mass without stiffness is very inefficient.


** The most effective *soundproofing* material you can get is lead sheet
added all over a plaster or timber wall. Lead sheet adds huge mass and a
little damping.

Otherwise, replace the offending wall with a nice brick one - has huge
mass and stiffness.

Noise barriers built near the road seem to work.

http://www.fhwa.dot.gov/environment/keepdown.htm

 

[Paul Hovnanian P.E.]

James Varga wrote:

Okay - I have an idea here that I wanted to get soem feedback on and
hopefully some help with the circuit design.

I live by a really noisy road and wanted to try and build a noise
cancellation device. Kind of like what they use in some high-end cars. This
would be placed facing the window where the noise comes from and
essesntially read the sound - invert it - and play it back.

I'm guessing it would need to focus on the lower end of the spectrum as the
higher-end would get stopped by the window. (well most of it).

This is probably correct.

When analyzing the noise situation, it might be helpful to identify how
the noise is getting into the structure. If the noise is being conducted
through the ground, some sort of base isolation may be needed between
the footings and floor joists. If the noise is being conducted through
the walls, adding mass and/or damping to the wall may help. In addition,
noise conduction through framed walls can be reduced by building a
double wall. In effect, an inner wall with its own studs not attached to
the outer wall will keep vibration of the outer wall from being
conducted to the inner wall.

--
Paul Hovnanian mailtoaul@Hovnanian.com
------------------------------------------------------------------
c (velocity of light in a vacuum) = 1.8x10^12 furlongs per fortnight

 

[Pooh Bear]

Phil Allison wrote:

"N. Thornton"

Adding mass without stiffness is very inefficient.


** The most effective *soundproofing* material you can get is lead sheet
added all over a plaster or timber wall. Lead sheet adds huge mass and a
little damping.

Otherwise, replace the offending wall with a nice brick one - has huge
mass and stiffness.

Mass is really the only thing that really stops sound effectively, esp at low
frequencies.

A friend of mine once made a 'soundproof' door - it was about 5" thick and
filled with sand ! It worked very effectively. It also needed industrial
strength hinges and a castor support at the outside edge..

Graham

 

[Watson A.Name - \"Watt Su]

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:416F166C.88942DB5@hotmail.com...

Phil Allison wrote:

"N. Thornton"

Adding mass without stiffness is very inefficient.


** The most effective *soundproofing* material you can get is lead
sheet
added all over a plaster or timber wall. Lead sheet adds huge mass
and a
little damping.

Otherwise, replace the offending wall with a nice brick one - has
huge
mass and stiffness.

Mass is really the only thing that really stops sound effectively, esp
at low
frequencies.

A friend of mine once made a 'soundproof' door - it was about 5" thick
and
filled with sand ! It worked very effectively. It also needed
industrial
strength hinges and a castor support at the outside edge..

Graham

You mean caster?

https://www.cheyennemountain.af.mil/

 

[Pooh Bear]

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:416F166C.88942DB5@hotmail.com...

A friend of mine once made a 'soundproof' door - it was about 5" thick
and
filled with sand ! It worked very effectively. It also needed
industrial
strength hinges and a castor support at the outside edge..

Graham

You mean caster?

Maybe in the USA ?

I would use caster for sugar personally.

" caster or castor
As applied to the sugar sprinkler and the swivelling wheel on furniture, the
words can have either spelling: Caster sugar is finely ground white sugar;
It can be difficult to move a bed if it is not on castors.
Castor oil, however, has only the one spelling. "

http://www.tiscali.co.uk/reference/dictionaries/english/data/d0081712.html

Graham

 

[Phil Allison]

"Pooh Bear"

That would certainly work! Loose sand has damping as well as mass,
which confuses the demonstration somewhat. If you take a look at the
BBC developed soundproofing panels you'll see they are lightweight.

I'll bet they're good at midrange and HF but rather poor at LF. Rockwool
sheet has similar characteristics.

** Being portable panels they have no attenuation of low frequencies at
all. Good enough to reduce speech to background levels in an office maybe -
but offices have high backgrounds.




................. Phil