Date: Tue, 16 Jan 2001 12:59:27 -0700
Reply-To: Keith Adams <keith_adams@TRANSCANADA.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Keith Adams <keith_adams@TRANSCANADA.COM>
Organization: TransCanada
Subject: Re: road trip report - Calgary/Seattle
Content-Type: text/plain; charset=us-ascii
WHAT?? I CAN'T HEAR YOU! IT WAS A LONG TRIP!
I should have been more specific I guess...
I used C-weighted line, slow meter response. I used a Realistic model
33-2050 sound level meter. According to the noise control engineers
here at work (who I borrowed it from) said it performs very favourably
with their mega dollar digital equipment they have. This meter does
have A and C lines, fast and slow response. Also an output to a
recorder (no idea how to use it).
I wasn't trying to get everyone into a panic that driving a vanagon is
going to cause hearing damage (my apologies for boggling the definitions
for threshold of hearing damage!). Just trying to relate that the sound
levels in the van are quite high, even without 4 12" subs and 2500W
driving them. I'm just trying to establish a baseline to gauge
reductions in road noise due to various sound proofing treatments. Thus
why I used full spectrum C weighting. And the stupid thing is, I never
did a check at idle. Oh well, I think I'm going to buy one of these
babies for use in setting up my home theater anyways.
"C-weighting is nearly uniform over the frequency range 32 Hz to 10 kHz,
thus giving an indication of the overall sound level. The A-weighting
responds primarily to frequencies in the 500 Hz to 10 kHz range, which
is the area of greatest sensitivity of the human ear." (quote from the
owner's manual).
I want to be sure that I can get the overall sound levels down.
Without an accompanying spectral analysis, neglecting the frequencies
below 500 Hz (which is still a fairly high frequency - I'm sure the
droning of tires is in that range) might be missing something. Anybody
have a spectrum analyzer they'd like to pass on for free? =)
Thanks for catching that David.
Keith
David Beierl wrote:
>
> A-weighted or C-weighted? Only the A-weighted number is valid for
> hearing-damage purposes...(C-weighted is flat, A-weighted rolls off the low
> end considerably). Also, was it a $30 Radio Shack meter like mine, or a
> "real" one (there are $250 meters available, but to do OSHA industrial
> measurements you need the $1200 one as I recall (all prices about 15 years
> old...).
>
> I think it would be great to use the RS meter since they're cheap,
> available everywhere, and I *think* fairly consistent from meter to
> meter. Also it would be good to have both C- and A- numbers, also possibly
> fast and slow meter damping (four readings in all).
>
> david
