New exhaust noise rules

**Ocean1** · 22nd June 2008, 09:16

Originally Posted by Gremlin

hmmm i wonder how you go about getting a free idea of how loud it is... from memory, my old bike went over 100db at idle, and wasn't loud.

Unless it idled bloody fast or was powered by a scramjet I very much doubt the old bike made 100dba at idle.

The scale is logarithmic wrt the quantity of energy involved. Our perception of the sound is also non-linear, most of us perceive a six to ten dB increase to be about a doubling of “loudness”, changes of less than about three dB are not really noticeable.

Leme see…

Here: http://www.gcaudio.com/resources/howtos/loudness.html

**Gremlin** · 23rd June 2008, 02:30

Originally Posted by Ocean1

Unless it idled bloody fast or was powered by a scramjet I very much doubt the old bike made 100dba at idle.

nope, was normal... around 2-3000 rpm hit levels around 107db...

reading the pdf very carefully, (relevant guff starts around pg 10) the key points for a 4 stroke 4 cyl (ie, zx10) would be 0.5m away from pipe, at a 45 degree angle, at least 200mm off the ground, and at 4500rpm (not including environment conditions). Looks like I will have pull the mobile out, and get another reading, as I think I measured directly behind the pipe, but at distance. There is also mention that the microphone has to be insulated with a foam windshield during test, so it isn't direct, and a more ambient sort of measurement (section 2.8(3) a) )

However, there is an extra kicker. Section 2.8(8) makes provision for "multi-mode exhaust systems" - which I basically read that removable baffles would be removed as well, or would seem likely. In that case, it would appear you are measured on the loudest measurement (most likely the baffle out).

This also makes sense as the system is then stickered for compliance, and appears to remain active until the system is modified. It would appear you can't comply with the baffle in, then remove it

(because of the rule above, about how a measurement is taken, as they wouldn't be able to sticker the system in a way to prevent you removing baffles)

Basically, I would rather be proactive, than have bad cops constantly shit stirring for extra annoyance, or being green stickered resulting in extreme inconvenience. Does also make it tempting however if the cop is nasty, and despite compliance makes you do another test. On passing, I would be invoicing the police for the lost time to the company on an hourly basis... rather not start that shit fight tho.

**ajturbo** · 23rd June 2008, 06:40

Originally Posted by 98tls

Could get very annoying for those of us living in small towns with a copper that has a problem with motorcycles.Irrelevant of how noisy the bike is its a huge pain in the arse to get it to the nearest place that can test it.

but i used to think oamaru was such a big place....

**boomer** · 23rd June 2008, 08:29

Originally Posted by Gremlin

nope, was normal... around 2-3000 rpm hit levels around 107db...

Man, your full of shit.

100dB's at idle my ass...

**Tank** · 23rd June 2008, 10:33

I wonder how they get on for bikes with no RPM gauge.

If your bikes borderline - how can the prove that it fails with no way of accurately measuring the rpm?

**slimjim** · 23rd June 2008, 11:19

nope 100 is good, loud enough to save lifes

**vifferman** · 23rd June 2008, 12:01

Originally Posted by slimjim

nope 100 is good, loud enough to save lifes

But not the baby fur seal whales?

**scumdog** · 23rd June 2008, 12:11

Originally Posted by slimjim

nope 100 is good, loud enough to save lifes

That ranks right up there with "Lets have a KB wave" statement.

**Mikkel** · 23rd June 2008, 12:21

Originally Posted by Ocean1

The scale is logarithmic wrt the quantity of energy involved. Our perception of the sound is also non-linear, most of us perceive a six to ten dB increase to be about a doubling of “loudness”, changes of less than about three dB are not really noticeable.

An increase of 3 dB is equivalent to a doubling of the intensity.

The low-down on decibels. And sound pressure.

A 100 dB is a loud exhaust. Most racetracks have a 90 or 95 dB limit (I think the signs at Ruapuna says 95 dB limit). However, it is also important where the measurement is taken. Is it at 1 meter, 1 mm or 1 km from the exhaust? It would have to be consistent to make any sense in the first place.

**Morcs** · 23rd June 2008, 13:47

Just as well I have the baffle still in on the dr's yoshi....

with it out, its a shite site louder than my TL with a set of Two bro's...

Hopefully this law will nail the suckers in shite cars with their exhausts - im sure theyll replace them with louder duf-duf stereos though...

**skidMark** · 2nd July 2008, 20:59

Originally Posted by Morcs

Just as well I have the baffle still in on the dr's yoshi....

with it out, its a shite site louder than my TL with a set of Two bro's...

Hopefully this law will nail the suckers in shite cars with their exhausts - im sure theyll replace them with louder duf-duf stereos though...

Hey man, my honda civic we used to roll to pool in was awesome.

My chick mate who bought it totalled it into the back of a van on the motorway like a month ago though.

I blame the cut springs.

**scumdog** · 2nd July 2008, 21:50

Originally Posted by Morcs

Hopefully this law will nail the suckers in shite cars with their exhausts - im sure theyll replace them with louder duf-duf stereos though...

Don't worry - they CAN be nailed for that too...

**R6_kid:Me** · 2nd July 2008, 22:19

Shares in racefit exhausts just went down 5 points!

**Sanx** · 2nd July 2008, 23:25

Originally Posted by Mikkel

A 100 dB is a loud exhaust. Most racetracks have a 90 or 95 dB limit (I think the signs at Ruapuna says 95 dB limit). However, it is also important where the measurement is taken. Is it at 1 meter, 1 mm or 1 km from the exhaust? It would have to be consistent to make any sense in the first place.

Most racetracks have a sound limit at the boundary. Your bike cannot produce any sound that exceeds the set dB rating when measured at the edge of the racetrack's property.

Given that the spl decreases with distance, 100dB at 0.5m is nowhere near comparable to 95dB at 10 metres or so. I wouldn't be surprised if the 100dB at 0.5m rule got quite a lot of bikes...