Re: Triggered gap-LOUD

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

In sound isolation you have two problems:
air paths - sealing is the key.. small slots let amazing amounts of sound
through
transmission through the panel - mass and non-stiffness is the key - hence
the popularity of lead sheet, massive, soft, etc.

Foam, fiberglass batts, etc. are nice at killing HF reflections or
transmission (which is probably where most of the noise from a spark gap is)
because the wave gets bounced around off all that stuff and gradually gets
attenuated.  If you want to kill the sound of talking from the next room,
this is the hot ticket, because it is cheap and compatible with usual
drywall and stud construction.

However, that stuff doesn't work for beans at low frequencies (say below a
few hundred Hz), where panel vibration is the problem.

You sort of have a set of choices: very stiff panels (so the incident wave
doesn't make the panel vibrate), massive panels (concrete walls), or very
lossy panels (lead sheet).  Other popular techniques are sand filled panels
(however, eventually, the sand packs down from vibration), various massive
materials in sheet form (there are a whole raft of elastomers and composites
loaded with everything from sand to iron filings or iron ore (cheap,
powdered form is easy to get, iron oxide is pretty inert, and it's dense).
The loaded plastics are popular because they are massive (so it doesn't move
much for a given amount of "push" from the incident sound wave) and lossy
(because they are particles in a soft matrix, so there is high viscous loss
when the particles DO move).

For a spark gap, I'd work real hard on making sure there are no air gaps.
When fooling with some exploding wires, I discovered that concrete blocks
with a rubber gasket worked real well at killing the gunshot like noise.

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, October 20, 2001 5:09 PM
Subject: Re: Triggered gap-LOUD


> Original poster: "Luc by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<ludev-at-videotron.ca>
>
> Hi guy,
>
>
> The stuff Robert describe sound promising I think, It need to be
> try and may be I could share some information too.
>
> Couple of years ago I made contact with a soundproofing company
> for new studio at job, I spoke a lot with the engineer they send.
> The guy tell me that the best material he know is lead sheet
> sandwich between compress glass wool they have different
> thickness of lead sheet the thicker the better they have lead
> charge rubber too less expensive but less efficient too. I saw in
> Edmund scientific catalog I think 2 or 3 years ago a special
> rubber that convert sound wave energy in heat.
>
> Cheers,
>
> Luc Benard
>
> snip
> >
> > Foam rubber packing with rough a surface like an egg carton is about the
> > best sound absorber you can get. I used it to line my basement gun room
so I
> > could shoot 30-06 and 12 ga in my house in the winter with out bothering
my
> > family with noise. It worked very well. I'm quite shure if it  will stop
06
> > noise it will supress a spark gap pop.
> >      Robert H
>
>
>