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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