Date:         Sat, 23 Oct 2004 11:11:50 -0700
Reply-To:     Reinhard Vehring <rvehring@YAHOO.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Reinhard Vehring <rvehring@YAHOO.COM>
Subject:      Re: noise reduction
In-Reply-To:  <6.0.3.0.0.20041023072826.03865360@buncombe.main.nc.us>
Content-Type: text/plain; charset=us-ascii

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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