Norton Decibles

Here in New Hampshire they arre about to pass a law reducing the permissible motorcycle decibles from 106 t0 96 wile idling.
Now I dont think standard Norton silencers even approach that, but I am curious to know just what the average decible levels are.
My MK3 is fitted with the "bean can" silencers, which I think are even quieter than the pea shooters. Anybody ever measure theirs?

hello,
it is hard to imagine using stock exhaust {peashooters} that a norton would ever be as loud as most harleys blasting up the road. I have a few friends with harleys and when I drive directly behind I can't hear myself think. Just as annoying at idle. So I don't think u have anything to worry about unless u have modified your exh system. like just headers and no silencers
Dox

I 2nd Doxford, Nortons are so pleasantly soft at idle they are not noticed in normal traffic sounds, only quiet woods most the rallys take place. Giving high throttle of course gets them noticed but not in painful obnoxious way the big twins do that shut down conversations till a mile away. One can be a bit timid in the areas one might get noticed of course. Here's real world example list of db's to judge by if not going by a stereo or music shop with a db meter.
http://www.industrialnoisecontrol.com/c ... amples.htm

The 1974 JPN Special with Mark 2A mufflers and airbox registered 80 db (A) in the Cycle magazine test.
This was a moving test, I think at 30 mph under load.

The factory sound level tests were done with a 22 tooth sprocket in order to reduce the revs and sound levels.
The 22 tooth sprocket was associated with layshaft bearing failure somehow.

I'm interested to see how the motorcycle at idle measurements will be done.

About the only place sound is measured in public in Arkansas is at the big biker festivals in towns that get you noticed while police around with meters, who will pull you over to measure and ticket. Otherwise a non issue even on too loud bikers that are behaving w/o showing off. Call the STATE DMV and ask how they intend to monitor sound levels. The baffled black can mufflers are known to stifle the Norton Torque response and require jetting changes from plain peashooters.

My Mk2A also came with the bean cans and I agree they are definitely quieter than the peashooters. But I'm interested in how NH intends to enforce this? Are they planning to force the inspection stations to do it? I know New Hampshire has some draconian inspection laws for bikes (I thought PA was bad until I read yours), but I didn't see anything about noise testing.

I'm just curious because I own an inspection and emission station in PA and every time the state decides there is something else vehicle-related that we all have to be saved from, it falls to the inspection stations to pay for the equipment/training to do the appropriate tests.

It seems to be a Norton trait that the idle and low rpm is subdued while once up on the cam they get a real snarl on.
My Commando with the open peashooters is that way as is the 650 SS with stock pipes and mufflers.
It allows one to tiptoe around if needed, while still having a bike that really lets you know its there when the throttle is opened.

Glen

this is exactly why I try to talk some sense to the straight pipe idiots. like I have told them, if you don't police your self's than you wont like it when the state steps in. another one I like is " if loud pipes save lives think what learning to ride it would do "

L.A.B. said:

http://articles.boston.com/2012-03-09/metro/31136335_1_motorcycle-noise-loud-pipes-loud-motorcycles

Click to expand...

FWIW Radio Shack sells a decibel meter for $50 http://www.radioshack.com/product/index.jsp?productId=12680845
have one myself but have not checked my bike with it

tban52 said:

Here in New Hampshire they arre about to pass a law reducing the permissible motorcycle decibles from 106 t0 96 wile idling.
Now I dont think standard Norton silencers even approach that, but I am curious to know just what the average decible levels are.
My MK3 is fitted with the "bean can" silencers, which I think are even quieter than the pea shooters. Anybody ever measure theirs?

Click to expand...

I'm in Chesterfield, NH and this is probably the only good law that the legislature has passed this year. I'm not anti-Harley nor do I dislike Harley riders but the idiots with the straight pipes are more than annoying. I have to listen to them all summer and there isn't one thing good that you can say about the sound. The damn things are simply loud and don't even come close to the wonderful sound of a Norton when you're going through the gears. I'm also considerate of others and if its early in the morning or I'm in a clearly residential area I watch my gearing so as not to disturb people more than is reasonable. I just wish most Harley riders were as considerate.

Also, if memory serves me when Norton's were being sold back in the 70's a lot of states had noise regulations more stringent than this and standard peashooters could meet it without a problem.

When I was working in Norton's R&D group, we had to get the Commando to meet the US regs for noise. It took a LOT of work and money. The Harleys I hear around here every day are nowhere close!

There were two tests, IIRC. One was a full throttle acceleration in second gear past a pair of calibrated microphones about 100 yards apart, running the bike in parallel with the microphones. The other was a high speed run at maybe 80% of the bike's top speed past the same microphones. We did the testing at the Motor Inustries Research Association facility near Nuneaton. We managed to get the acceleration noise below the regulatory limit, but the mufflers were quite restrictive.

The high speed pass was a different ball game. We had to do a lot of analysis, since we failed frequently. In the end we found that the airflow through the engine cooling fins was the predominant noise. I think the angle at which the engine was installe may have contributed to the problem, since the airflow was forced upwards.

I'd left N-V before the final solution to the problem was developed.

As I remember, the Commando was one of the quietest high-performance bikes on the planet, though later BMWs and Gold Wings beat it. I'm gob-smacked that some of the bikes currently sold are allowed to be so noisy, after N-V spent so much money trying to meet the US regs. Maybe the regulations have been relaxed since the late 1960s.

I don't remember the specific dB levels we were working with, but I think the full throttle test limit was around 100 dB. Most current HD's must be around 120dB even on relatively gentle accelerations at part throttle. When the Oyster Run is in town, the noise is incredible.

JimR said:

tban52 said:

Here in New Hampshire they arre about to pass a law reducing the permissible motorcycle decibles from 106 t0 96 wile idling.
Now I dont think standard Norton silencers even approach that, but I am curious to know just what the average decible levels are.
My MK3 is fitted with the "bean can" silencers, which I think are even quieter than the pea shooters. Anybody ever measure theirs?

Click to expand...

I'm in Chesterfield, NH and this is probably the only good law that the legislature has passed this year. I'm not anti-Harley nor do I dislike Harley riders but the idiots with the straight pipes are more than annoying. I have to listen to them all summer and there isn't one thing good that you can say about the sound. The damn things are simply loud and don't even come close to the wonderful sound of a Norton when you're going through the gears. I'm also considerate of others and if its early in the morning or I'm in a clearly residential area I watch my gearing so as not to disturb people more than is reasonable. I just wish most Harley riders were as considerate.

Also, if memory serves me when Norton's were being sold back in the 70's a lot of states had noise regulations more stringent than this and standard peashooters could meet it without a problem.

Click to expand...

I'm in a very quiet rural area also, and on summer nights you can hear the loud bikes out on the main road for miles and miles. I try to sneak out in 2nd gear till I reach the main road on my early morning runs, and I'm at the bottom of a hill so it's easy to "coast" home.

I'm in New Hampshire, (lakes region). Used to work for MAX BMW and BCM Ducati (parts, not tech), and have seen a few tested over the years. I don't think a Norton with stock pipes will have issues (if it isn't exempt) NH has always required the decibel tests for inspection, but many testers don't hold the meter to them unless it sounds close even though they are supposed to check every one. We had some Ducati's with aftermarket pipes that came close (clutches were sometimes louder than the pipes :mrgreen: ), and some that the owners installed stock mufflers for the test and went back to the loud pipes after inspection. The owner can still be ticketed by police for loud pipes, but from what I was told. I can't recall the exact numbers, but for twins, IIRC, the test was to hold the meter approximately 1 meter from the end of the muffler at a slight angle away and rev the bike to 3k RPM's (singles and multis have different RPM requirements).

RSR

I have followed this sound reg story in NH since I first read about it in the AMA magazine. I think we all knew this was coming due to the knuckle dragging neanderthal, open pipes, look at me mentality of some riders.

I live at a fairly large lake in PA that is a popular riding destination. In the summer the noise can be deafening sometimes. I love the rumble of a well tuned twin, no matter what the configuration but these guys are just obnoxious.

As usual, due to a few thoughtless boneheads, the rest of us will pay. I imagine PA will be next in line with the noise regs. Just my .02 :x

This is a messy subject to talk about in definitive terms.

It is all about measuring standards. If you read various country standards there is a lot of detail about meter location, distance and angle from the exhaust, instrament standards and calibration, other objects in the immediate area, other sources of noise in the area, corrections for pressure humidity etc etc. The standard spec often goes on for pages.

But the main issue is how far from the exhaust is the meter. 0.1 metres, 1.0 m, 10 m, 100 m, etc.

So there isnt an answer to the origional posters question unless someone can specify the measuring methodology.

What I can say is that in NZ Classic racing we are restricted to 95 db and this is usually measured about 30 m from the edge of the track where the bikes are under full acceleration. There's also another method which involves the bike stationary with the engine being run at a specified rpm with the meter set at the correct distance and angle from the exhaust. I dont know the exact spec for this.

And beleive me this noise monitoring causes real issues. Not the least of which is that the local "inspectors" dont seem to have read the NZ measurment methodology standards. I got into this in my job working in the oil industry because we were spending millions silencing rigs. So we really did make sure we knew the standards. But most local authority officers have very little clue about what they are doing.

Some bikes have big issues meeting the specs. Triumph and BSA triples with 3 into one exhausts have a terriable time.

But Nortons are usually ok with silencing cans on a megaphone exhaust and Im sure a Commando with peashooters would pass under our rules.

So unless the New Hampshire regs say the meter is less than 1 metre from the pipes then at idle you should be fine.

Incidently one of the big issues in meeting the NZ regs depends on your cam timing. If the cam has very wide timing or is very advanced over standard the exhaust note gets really sharp.

This website gives examples of noise levels

http://www.industrialnoisecontrol.com/c ... amples.htm