Would be interesting to take a refrigerator box and cut out a full partition to put behind the front
seats and measure sound with it in place.

----- Original Message -----
From: "Garth Woolstenhulme" <garth@RGLOBAL.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Sunday, October 24, 2004 12:02 AM
Subject: Re: noise reduction

Ten years ago I took my aluminum cans in the van to be recycled.  I had
been collecting them in 40 gallon trash bags and when it was time to put
them in the Vanagon, there were so many I had to really cram them in the
van (BTW, these were all soda cans I had collected at work -- sounds
like I have a real problem with that many empties).  But on the way to
the recycler I could not believe how quiet the van was.  All I could
hear was the noise of the tires on the road.  I had to turn off the
radio and just listen.  It was very pleasant.  I have always felt after
that time that the majority of the interior noise comes from the rear of
the van.  Other than driving around with a van stuffed with aluminum
cans, I have always wondered how to cut the noise from the rear.
Garth

Reinhard Vehring wrote:

>Here are some more measurements as promised:
>I taped the leading edge of the driver door with duct
>tape to the a frame, so that there is no gap at all
>left. Then compared that to the noise level without
>the tape. About a 3 mile stretch of highway, done in
>both directions, 2 times. Subjectively, I'd say, there
>is a little less wind noise with the tape in place,
>but the measured difference was very small maybe 1
>dBA, pretty insignificant. I guess you can leave your
>doors in :-)  This is not the main source of noise.
>Again, at 65 mph the quality of the road surface made
>a bigger difference. Hitting rough spots easily means
>+ 3 to 4 dBA, driving over the raised lane marker
>bumps: 88 dBA!
>I also did some measurements using the c-weighting.
>(The A-curve is a wide bandpass filter centered at 2.5
>kHz, with ~20 dB attenuation at 100 Hz, and ~10 dB
>attenuation at 20 kHz, it tends to heavily roll-off
>the low end, with a more modest effect on high
>frequencies. The C-curve is "flat," but with limited
>bandwidth, with -3 dB corners of 31.5 Hz and 8 kHz,
>respectively) If the noise is primarily low frequency
>the dBC reading is much higher than the dBA reading.
>The result: 95 dBC / 80 dBA at 65 mph. Lot's of low
>frequency noise.
>It's not the tire profile, I think: 65 mph is about 29
>m/s. Tire circumference is about 2 m, 60 profile
>blocks around makes about 900 Hz noise frequency.
>That's not it. dBA and dBC are practically the same at
>900 Hz.
>Well anyways, I have to stop the hunt for noise for a
>few weeks. My job is getting pretty busy :-(
>Take care
>Reinhard, 83 Westy, "Moose"
>
>
>-- Edward Maglott <emaglott@BUNCOMBE.MAIN.NC.US>
>wrote:
>
>
>
>>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.
>>
>>
>>
>...
>
>
>
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