View Full Version : Db of your exhaust?
VYSSion
02-08-2007, 02:58 PM
Has anyone had their exhaust Db reading taken? I think the legal limit is somewhere around the 88-90db, is that right?
I've just had the large rear resonators removed from my twin 3" Difilippo system and replaced with a pair of very slimline hotdog style ones. The reason for the change for me was the original system sounded great at idle, but as the rpm's got higher the exhaust note seemed to disappear and all I could hear was the engine noise.
Now with the hotdogs in it sounds MUCH meatier all the way through the rev range, much happier. Plus I've kept the old mufflers just in case I need to get over the pits.
The final Db reading I got was 99.3db at a distance of 3M at 3000rpm - which apparently is the regulation conditions. A little over the legal limit, but it doesn't sound over the top. :)
RED R8
02-08-2007, 03:03 PM
Oh no another Perth Vy owner that will end up with every conceivable bolt on accessory and every exhaust configuration know to man AT LAST a buddy for Daz.
2 cylinders shy
02-08-2007, 03:08 PM
If the legal limit is 90 then your only eight times louder than legal, mmmm nice
VTR8Clubby
02-08-2007, 03:10 PM
Just curious where you got the reading done?
I would like to know how loud mine is so I know how careful I have to be when there's cops nearby.
RED R8
02-08-2007, 03:26 PM
If the legal limit is 90 then your only eight times louder than legal, mmmm nice
Wouldn't 720db be eight times the legal limit.:confused:
chrism697
02-08-2007, 03:32 PM
Wouldn't 720db be eight times the legal limit.:confused:
No,
the way db are measured is 1db is roughly the quietest a human ear can hear, 2 db is double that, 3 db is double again then 4 db is double 3db and so on. 100db is double the sound of 99db anyway you get the idea
an example of this is jet engine is around 120db i think (a rough guess) it doesnt mean its only 30% louder than a V8 commodore sitting at 3000 rpm
anybody feel free to correct me, as im not 100% sure but i believe that is how it works
HARMSY
02-08-2007, 03:35 PM
Wouldn't 720db be eight times the legal limit.:confused:
Thats what one would think, had mine done by an EPA bloke i knew.....read 90db at idle and then 101db at 2800RPM, i'm like sweet that's not too bad.....his response, Ahh thats actually about 10 times over the limit :confused:, he tried to explain the reasons, but it went straight over my head.....
1000kw
02-08-2007, 03:37 PM
Beat me too it chris, decibel increases are expediential.
UTE = 98db @ 4,000rpm.
brentonsav
02-08-2007, 03:37 PM
Wouldn't 720db be eight times the legal limit.:confused:
daz, from memory back in vce physics days its a logarithmic relationship
here you go... from my VCE notes...
Example: What is the change in intensity level if the sound intensity is doubled?
Solution: Using L = 10log10(I2/I1) = 10log10(2I1/I1) = 10log10(2) = 3.01dB.
Example: What is the change in intensity level if the sound intensity is tripled?
Solution: Using L = 10log10(I2/I1) = 10log10(3I1/I1) = 10log10(3) = 4.77dB.
You get the idea... :)
PS.
Source - Intensity level (dB) - Intensity (Wm-2)
Threshold of hearing - 0 - 1x10-12
Leaves rustling - 10 - 1x10-11
Library reading room - 30 - 1x10-9
Talking to someone - 65 - 3.2x10-6
Street traffic - 70 - 1x10-5
Siren - 100 - 1x10-2
Thunder - 110 - 1x10-1
Threshold of pain - 120 - 1
Jet engine - 130 - 10
ziggycv8z
02-08-2007, 03:41 PM
On the decibel scale, the smallest audible sound (near total silence) is 0 dB. A sound 10 times more powerful is 10 dB. A sound 100 times more powerful than near total silence is 20 dB. A sound 1,000 times more powerful than near total silence is 30 dB. Here are some common sounds and their decibel ratings:
Near total silence - 0 dB
A whisper - 15 dB
Normal conversation - 60 dB
A lawnmower - 90 dB
A car horn - 110 dB
A rock concert or a jet engine - 120 dB
A gunshot or firecracker - 140 dB
You know from your own experience that distance affects the intensity of sound -- if you are far away, the power is greatly diminished. All of the ratings above are taken while standing near the sound.
Any sound above 85 dB can cause hearing loss, and the loss is related both to the power of the sound as well as the length of exposure. You know that you are listening to an 85-dB sound if you have to raise your voice to be heard by somebody else. Eight hours of 90-dB sound can cause damage to your ears; any exposure to 140-dB sound causes immediate damage (and causes actual pain).
Here are some interesting links:
RED R8
02-08-2007, 03:51 PM
You learn a little everyday,thanks for explaining it guys.
brentonsav
02-08-2007, 03:56 PM
You know from your own experience that distance affects the intensity of sound -- if you are far away, the power is greatly diminished. All of the ratings above are taken while standing near the sound.
that is actually an inverse square relationship
HARMSY
02-08-2007, 04:10 PM
that is actually an inverse square relationship
My theory.....
90db /@##$ + #$% = Loud
100db /#$%&^ + $#@$% = Louder!
Simple :hide:
VYSSion
02-08-2007, 04:18 PM
I had the reading done next door to my work here at ARB in Osborne Park... it's called something or other Custom Exhausts. I just had a look out the window but I can't see their sign.
I know it's illegal... but technically so is an exhaust tip so i'm not too worried. Actually, there was a highway patrol sitting about 20m away while they were doing the test and they didn't bat an eyelid.
But seriously, thanks for the db lesson... I had no idea it worked like that either. :confused:
2 cylinders shy
02-08-2007, 04:46 PM
Wouldn't 720db be eight times the legal limit.:confused:
For every 3 decibels the sound doubles or so i thought.
I just checked google and actualy for every 3 decibels the sound is multiplied by 1.9953.
RED R8
02-08-2007, 04:49 PM
For every 3 decibels the sound doubles or so i thought.
I just checked google and actualy for every 3 decibels the sound is multiplied by 1.9953.
So does that make Marks sytem about 6 times the legal limit ???
maloo_
02-08-2007, 05:03 PM
My VK Brock got tested at 125db and friends VL Group A with quad webers was 140+ .EPA guy did'nt really like it .
swingtan
02-08-2007, 05:06 PM
try...
http://www.ls1.com.au/forum/showthread.php?t=77668
In particular page 2 where Wonky and I get a bit carried away. The dB measurement means is nothing without a reference as it's a measurement of change. A change of 3dB is the smallest you can hear, and a change of 10dB means the sound is twice as loud ( or half as loud depending on the direction of the change). So 99dBA ( which is what it should have been measured in as the regulations state 90dbA ) would see you with an exhaust that is almost 2x louder than the limit.
Simon
VYSSion
02-08-2007, 05:31 PM
I think I've learned too much today... other important info is falling out of my other ear. :confused:
RED R8
02-08-2007, 05:33 PM
I think I've learned too much today... other important info is falling out of my other ear. :confused:
The old filing cabinet is full you reckon.
Leilani7
02-08-2007, 05:42 PM
Low flying plane here, it just went straight over my head
VRROOMMMM!!!!!!!:confused:
I always did hate maths at school!!!:rofl:
ssgirl2
02-08-2007, 05:43 PM
Learn something everyday...but it doesn't usually hurt that much :bawl:
SS :D
:wave: Leilani...I reckon a fork in the nose would hurt less :lmao:
Leilani7
02-08-2007, 06:03 PM
:wave: Leilani...I reckon a fork in the nose would hurt less :lmao:
Or worse still, pulling it out again::nyuk:rofl:
:wave: back at you Kirst
BLACK 346
02-08-2007, 06:25 PM
Beat me too it chris, decibel increases are expediential.
UTE = 98db @ 4,000rpm.
Do you mean Exponential :)
Just curious where you got the reading done?
I would like to know how loud mine is so I know how careful I have to be when there's cops nearby.
There is only one way to drive when they are around, zero throttle
and hope they have the stereo up :)
Evening,
Do a search and you will find a thread that I started in relation to this.
FWIIW, the test criteria is, for LS1's 4500rpm, 500mm and at 45% from the exhaust tip!!
With twin 2.5, Tri Y's and an ESA system my thing went 106DB's!@!!!
Cheers,
Hogs,:)
OzExcalibur
02-08-2007, 10:33 PM
:wave: Leilani...I reckon a fork in the nose would hurt less :lmao:
ya think? :1peek:
http://i25.photobucket.com/albums/c74/XRPSP/image001.jpg
http://i25.photobucket.com/albums/c74/XRPSP/image002.jpg
ssgirl2
02-08-2007, 10:37 PM
ya think? :1peek:
:lmao:...That's it!!!
SS :bawl:
VYSSion
03-08-2007, 12:00 PM
The funny part is I didn't tell the wife I was having the exhaust changed yesterday, and despite the exhaust now being something like 6 times louder than it was before.... she didn't even notice. :rofl:
I do get a reasonable drone now between 1800-2000rpm... but I rarely cruise at that RPM any more so it doesn't really bother me.
It's funny though, people claim these massive "seat of their pants" kw gains from fitting exhausts and extractors and stuff - but I reckon most of the perceived gains is purely from the sound. I KNOW that my car doesn't have any extra power from changing a muffler... but MAN it feels a lot faster now that I can hear it more. :)
6.2L.Club
03-08-2007, 12:41 PM
Forkin hell ! That boght tears to my eyes just looking at it. Poor little fella.
All l know is it sounds like a V8 supercar through the tunnel and that my stereo is even louder than that ! :D :lmao:
vt350phantom
03-08-2007, 01:42 PM
The Decibel (dB) is actually a log unit used to describe the ratio of signal level.
Increasing the intensity of a sound by a factor of 10 increases the level by 10dB
VYSSion
03-08-2007, 08:21 PM
Here is a link to a wmv file for a before and after for my exhaust. The camera's a little close to the car so it distorts a bit, but you can hear the difference in note . You can also hear in the first bit when I raise the revs slowly you can hardly hear it... then how much better it sounds afterwards.
Vid here - about 2.8Mb (http://members.iinet.net.au/~heimar/exhaust.wmv)
BLACK 346
03-08-2007, 08:25 PM
Here is a link to a wmv file for a before and after for my exhaust. The camera's a little close to the car so it distorts a bit, but you can hear the difference in note . You can also hear in the first bit when I raise the revs slowly you can hardly hear it... then how much better it sounds afterwards.
Vid here - about 2.8Mb (http://members.iinet.net.au/~heimar/exhaust.wmv)
That is very stealthy for a cammed LS1, dont reckon you would
attract to many problems with that :)
VYSSion
03-08-2007, 08:57 PM
Yeah, Dan tuned it to perfection. :)
TAKEITEZ
03-08-2007, 10:26 PM
ahhhh...
can't hear it in the second half. the camera hates it!
i'll measure mine tomorrow... i have a db meter at home so we'll see how it goes... it is too loud i know that much but anyway... how much louder???
yours sounds bout as loud as mine - but yours has a tougher idle :(
i want a tough idle...............
YouTube - VY Maloo... Take 3 on the zorst (http://www.youtube.com/watch?v=r-T2rVUNpH0)
note - its not stone cold either... hehe... it'd been running for a fair while and was upto temp, but it steams a fair bit like that
VYSSion
04-08-2007, 09:33 AM
My idle is actually very tame considering there's a cam in there I reckon.
TAKEITEZ
04-08-2007, 02:06 PM
it is pretty sedate... but its more grumpy than stock...
and its go the go to match the noise too...!!!
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