Date:         Sat, 23 Oct 2004 08:16:38 -0400
Reply-To:     Edward Maglott <emaglott@BUNCOMBE.MAIN.NC.US>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Edward Maglott <emaglott@BUNCOMBE.MAIN.NC.US>
Subject:      Re: noise reduction
In-Reply-To:  <4179E19A.8090308@shaw.ca>
Content-Type: text/plain; charset="us-ascii"; format=flowed

I am following this thread closely, as the interior noise is one of the
main down sides for the vanagon to me.  I have tinnitus and am sensitive to
sounds in certain frequency ranges.

Observations:

Thanks Reinhard for working on this and taking actual measurements!  This
is key to finding real results rather than conjecture.

When fixing a little rust, I had the passenger foot well rubber pad
out.  This increased and changed the noise inside the front of the van
significantly.

The air that flows through the doors to the rear seating area vents is shut
off when you close the appropriate lever on the dash, so that is a good way
to test how much noise you save there.  (not much if any, imo.)

I believe most of the noise that annoys me is generated by the tires on the
road, and comes inside through the bottom of the van.  I believe this noise
is not transmitted mechanically through the suspension, but is just sound
waves hitting the bottom of the van and coming through.  I believe the
mechanical noise is much lower frequency, and doesn't bother me as much.

Wind noise is the other noise that annoys me most.  On a windy day I can
tell an obvious difference driving downwind or upwind.

The annoying sound for me is higher pitched than what comes from the engine
or exhaust.  It is a kind of whooshing, white noise sound.

If I stand by a highway, this is the predominant noise I hear.  I have seen
reports that show this is mostly tire noise.  As someone else noted, there
are road materials designed to be quieter, and You can experience this
switching from one road surface to another.  Seems like concrete is louder
than asphalt to me.

I know this weather strip at the leading edge of the front doors is not a
cure all.  That does seem like a prime area for a concentration of airflow
though.  I will have to look at a late model van to see what this looks
like.  Some folks have adapted some weather stripping from houses to help
in this area.  can Any of them comment on how this compares to the factory
set up?

I was looking at rubber membrane roofing for my house.  The material is
relatively cheap and is often used for lining ponds and other purposes
besides roofing.  I wonder if this would be a good material for
experimental wheel well liners?  Temporarily attach it with a few dabs of
silicone?

Keep up the good work.
Edward