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exhaust
Posted: Wed Jul 16, 2008 10:44 pm
by DavePatrol
my mates sirrra has a 2 inch straigt thro with just a hotdog and we did a dbs reading at tafe and it got 120dbs at 4000rpm and only went up 3 when reved to 7000rpm
Re: exhourst
Posted: Wed Jul 16, 2008 11:00 pm
by nicbeer
DavePatrol wrote:my mates sirrra has a 2 inch straigt thro with just a hotdog and we did a dbs reading at tafe and it got 120dbs at 4000rpm and only went up 3 when reved to 7000rpm
umm, u clicked the wrong button.
also 3db = twice as loud.
Posted: Thu Jul 17, 2008 8:02 am
by lay80n
Lucky the legal limit is 90db too. So with 3-4db being double the noise level, thats real legal.
Oh, and as nick said, try hitting reply, not new post.
Layto....
Posted: Thu Jul 17, 2008 8:44 pm
by Gwagensteve
Ahem, just to introduce some tech, 6dB is actually double.
120db is insane. Like I said int he other exhaust thread, a hot dog doesn't really drop the noise at all.
Steve.
Posted: Thu Jul 17, 2008 8:52 pm
by want33s
Gwagensteve wrote:Ahem, just to introduce some tech, 6dB is actually double.
Steve.
How does that work Steve?
http://www.phys.unsw.edu.au/jw/dB.html
Posted: Thu Jul 17, 2008 9:59 pm
by Gwagensteve
oops - doubleowned.
Steve.
Posted: Thu Jul 17, 2008 10:00 pm
by Gwagensteve
oops - owned.
I'm used to working in ultrasonics where we display sound waves 1/2 wave rectified, so imagine the waveforms displayed on the UNSW page but with the bottom 1/2 removed. In 1/2 wave recitifed signals, to double the signal
height takes 6dB.
Sorry...
Steve.
Posted: Thu Jul 17, 2008 10:09 pm
by BlueSuzy
OWNED again, Double post Gwagensteve
Posted: Thu Jul 17, 2008 10:17 pm
by Gwagensteve
If you were working on a wireless connection as slow as I'm on atm you'd be doubleposting too.
Steve
Posted: Thu Jul 17, 2008 11:06 pm
by want33s
I was sure it was only 3Db........
OK Steve we'll let you get away with a doublepost THIS time....
Jas.
Posted: Fri Jul 18, 2008 10:35 am
by PCRman
so we are agreed 10dB = double perceived loudness?
Posted: Fri Jul 18, 2008 11:15 am
by nicbeer
PCRman wrote:so we are agreed 10dB = double perceived loudness?
every 3db = twice as loud technically.
Posted: Fri Jul 18, 2008 11:48 am
by PCRman
nicbeer wrote:PCRman wrote:so we are agreed 10dB = double perceived loudness?
every 3db = twice as loud technically.
Sorry i disagree
3dB = twice as acoustically powerful or twice the sound insensity level (technically)
as defined in the graph here
http://www.phys.unsw.edu.au/jw/dB.html
loudness is by definition subjective and
"Experimentally it was found that a 10 dB increase in sound level corresponds approximately to a perceived doubling of loudness. "
so it takes 10 times the power to double the loudness
references
Fletcher, H. and Munson, W.A. (1933) J.Acoust.Soc.Am. 6:59
Robinson, D.W. and Dadson, R.S.(1956) Br. J. Appl. Phys. 7:166
Posted: Fri Jul 18, 2008 12:31 pm
by nicbeer
ahh thx. one way to add tech
we were both correct he he