[TheForge] Re: Sound proofing a shop

Fri Aug 12 11:04:34 EDT 2005

As I understand it, soundproofing with dead air uses the air as a
spring, more or less. If you have dead airspace in a closed area, the
sound hits one side of the air pocket and tries to make the air form
with the wave--but if the air is trapped it compresses and some of the
sound energy gets turned into heat. High frequencies compress the air a
very small amount per oscillation and so a relatively small pocket will
absorb the whole cycle--but low frequencies need a long spring to cycle
with the wave. Hence the big long baffle system for low end speakers or
sound deadening. The other option is mass, because the mass absorbs the
energy without transmitting it out out the other side. Same principle,
just a denser medium.

J

--- Mike Spencer <mspencer at tallships.ca> wrote:

> 
> BG> Dan's idea is correct, but stuff the gaps in between the studs
> BG> with fiberglass. Even this won't stop low-frequency sound... the
> BG> only thing that will stop that is mass.
> 
> Welll.... Some of you more technical guys can check me on this,
> but...
> 
> Low frequency sound, say in the 2 to 25 hz range, can be greatly
> diminished or eliminated with very large baffles.  Imagine a wall of
> concrete well crocks -- ca. 3' dia x 3' long -- stacked close-packed
> and 4 high so you can see through the wall.  Diameter and length
> affect the frequency of sound it will damp but I don't know the
> relationship.
> 
> My reference for this is my vague recollection a circa 1958 Science &
> Mechanics mag article about a guy who was building 6-foot diameter
> plywood whatsits that worked sort of like police whistles: high
> volume
> air, a large, flat box with a rotor that turned at X rpm.  Result was
> a infrasonic sound pulse at X hz, [0 < X < ~30].  Baffle walls made
> from large-diameter rings or tubes blocked the sounds he was
> generating.
> 
> I doubt this would work for impact sounds -- 400# ram whacking anvil,
> say -- because (I think?) such sounds have a broad spectrum with lots
> of high-frequency components.  And of course, it would have no effect
> on vibrations transmitted through the earth.
> 
> Jerry> You could always fill the walls with empty beer cans, they
> Jerry> would have some sound deadening quality and it would be fun to
> Jerry> do. In my case it's Diet Coke or Diet Pepsi.
> 
> You've heard about the house made from stacked embalming fluid
> bottles?  They're square in cross section and this mortician saved
> them up for years, then built a house.  Talk about a house that's
> quiet as a tomb...
> 
>       But the greatest bottle building of all is on the shores of a
>       lake near a little mountain hamlet called Boswell. David brown
>       was an undertaker living in Red Deer, Alberta who contracted
>       sleeping sickness because of the stress of his business. When
>       his doctor advised him to quit brown loaded his trailer and
>       headed west until he reached Kootenay Lake. Soon bored with
>       retirement, Brown got a job selling embalming fluid and kept
> the
>       empty bottles. He built his extraordinary house using 600,000
> of
>       them. Before he was half-finished, he was deluged with
> visitors.
> 
>       The two-storey house is 14 and a half metres long, and seven
>       metres wide, and laid out in a cloverleaf patter with circular
>       rooms. Insulation provided by the air trapped inside the
> bottles
>       is equal to that of a metre of glass-fibre matting. The house
>       reflects the sun and the waters of the lake.
> 
>       Brown died in 1970 but his son Eldon and his wife Diane Johnson
>       have kept the place open to visitors.
> 
>       http://www.galleries.bc.ca/agso/sites2.html
> 
> 
> J> Ah well. Wouldn't it be nice to be filthy rich? THink of all the
> silly
> J> things you could have....
> 
> And Bill Gates doesn't own even *one* steam hammer or 200 T press.
> Not even a 700# anvil AFAIK.  Imagine that.
> 
> Justin> Uh, start with "big" and "fast" and work your way up till you
> Justin> couldn't afford it anymore. Like, say, an f-18 on your own
> Justin> aircraft carrier.
> 
> The only time I ever got the hit with a pathologigical fantasy/desire
> for the Ultimate Big Toy was when I heard about a US Navy maintanance
> ship for sale.  On-board machine shop, foundry, forge, naval weapons
> shop, capability to take smaller vessels on board, some kind of
> floating drydock thing and other stuff I forget.  Essentially going
> for whatever was scrap price at the time -- penny a pound or
> something.
> 
> Roy> Around 30 years ago, I saw the ultimate "Screw the Joneses" in a
> Roy> rail station parking lot.
> Roy>
> Roy>    A Maserati *station wagon*.
> 
> Too bad you didn't snap a pic with your digital cam. :-)
> 
> When I first moved here in 1969, there was a Rolls Royce pickup truck
> parked out by a barn not too far away.  Having many other things to
> think about -- turning a wreck back into a house, two-year-old twins,
> trying to gadern in a new climate, setting up a forge in a woodshed,
> learning to live without electricity etc. -- I never got around to
> inquiring about it until it had disappeared and the old guy had died.
> I still wonder what the story was.  [And yes, I'm sure it, or at
> least
> the cab, was a Rolls.  I had just come from a couple of years as a
> foreign car mechanic.]
> 
> 
> 
> - Mike
> 
> -- 
> Michael Spencer                  Nova Scotia, Canada       .~. 
>                                                            /V\ 
> mspencer at tallships.ca                                     /( )\
> http://home.tallships.ca/mspencer/                        ^^-^^
> 
> -- 
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