Be interesting to know where the equipment is located (does every town have a set plus a trained operator?) and the time to get it to a location.
I know you can get a fairly accurate decibel level app for the iPhones. But no matter how accurate it is, I doubt it would be admissible in court with out millions in government testing and certifications.
The sound level will vary (by a lot) with distance and angle, so that alone would require some special equipment. Location also is a factor, because of echoes. A nearby wall or building will increase the noise level, for example. The microphone is also a factor.
A lot of those loud motorcycles are owned by Cops…we have a couple in our town.
When I lived in the Goffstown/Bedford area years ago and there were several cops who owned these very very illegal lifted trucks. No one paid attention until one of those trucks didn’t see the car in front of them had stopped and crawled right over the top of them - killing a mother and daughter.
The distance, angle, and rpm are all clearly defined in the law, and there are officers trained in the use of the db meter. Some towns that are emphatic about enforcement, such as Hampton, NH, train all their officers and equip most with meters. Many towns don’t care and have few if any meters or trained cops. The db meter itself is hand-held and can be purchased for under $500, an affordable purchase for law enforcement.
Some Harley’s also sound a lot better than others. We have a great muffler shop in town that “tunes” exhausts for a mellow sound that’s pleasing to the ears. He specializes in pickup trucks but he also does motorcycles and cars. When you hear a great sounding vehicle…his shop probably worked on the exhaust system. The difference is amazing.
Just ride up 1A from Seabrook north during tourist season and you’ll quickly find the towns that are serious about noise abatement.
They are supposed to check exhaust during annual safety inspection. What I have found is that they run it up and if it APPEARS loud, they check for the proper marking on the pipes, usually stamped into the pipes by mfr. Any question, they pull out the meter. I don’t own a Harley and Seacoast Harley will not do annual inspection on anything but Harleys so not sure about their process although few bikes coming and going from there are quiet 
Some exhausts are louder than a Harley:
Harley riders lament that since fuel injection, the classic potato-potato sound at idle is gone. I’d think a PCM with the right programming could manipulate the injectors to reproduce it. Call it the “potato chip.”
;-]
I’m curious how HD’s fuel injection system made any significant change in the engines odd fire exhaust.
Has HD redesigned their bottom end?
I'm curious how HD's fuel injection system made any significant change in the engines odd fire exhaust.
As I understand it, the small, close-coupled intake manifold allowed pressure pulses to disrupt the carb’s flow at idle. FI solved that. The odd (315/405 degree) firing interval is just part of the equation. When I hear a Harley go by slow enough to hear the separate pops, it sounds pretty even-firing to me.
Even though my hearing isn’t as clear as it was a few years ago the distinctive sounds of John Deere 2 cylinders, Pratt-Whtiney radials and Harley Davidson V twins are still unmistakeable. The Harleys are most noticeabe when throttling up at low rpms. Once they are cruising at a relatively high rpm with mufflers intact the odd firing becomes less noticeable.
I have driven old flat head 45 and 48 ci HDs with single mufflers that were relatively quiet and the odd fire exhaust wasn’t nearly as obvious as newer models. And an old police model was downright quiet.
Here’s the Harley sound pattern under load (not at idle with carb):
XOOOOOOXOOOOOOOOXOOOOOOXOOOOOOOOXOOOOOOXOOOOOOOOXOOOOOOXOOOOOOOOX
Compared to my '75 Norton 850 with 360 degree firing intervals:
XOOOOOOOXOOOOOOOXOOOOOOOXOOOOOOOXOOOOOOOXOOOOOOOXOOOOOOOXOOOOOOOX
Pretty close.
Does the Harley sound like poTayto, poTayto, poTayto, or poTahto, poTahto,poTahto?
Well, they finally said “let’s call the whole thing off” just like the song said.
@“Rod Knox”, I had a similar experience. I was driving home on I-95 and encountered slow traffic. It turned out that 4 motorcycles had all 4 lanes blocked. They would slow to about 40, then take off on the rear wheel for a mile or more. Then they would slow and play the same game again. I called 911 to report what seemed to me a very unsafe practice. The police officer on the other end of the phone couldn’t have cared less about this group of fools. I could tell by the conversation that she was probably not taking any notes and would forget about it as soon as she hung up. It’s hard to take the State Police seriously when they don’t seem to care about highway safety.
I have wondered about two modifications:
The first is if the cam timing is changed for the exhaust release so that the exhaust valve opens when the cylinder pressure is 120 psi or so instead of 60 psi at stock settings. I am using these numbers as possibilities. Most of the expansion has taken place by about 135 degrees ATDC so the power loss is minimal but the noise capablity increases substantially.
The second is in the form a question. Is there some way that the exhaust can be made to “blatter” with closed throttle? I can’t tell if the offfenders are carburated or injected. I was thinking maybe a second spark to the cylinders late ATDC to ignite a burnable mixture in the exhaust system. I have noticed the same effect in custom cars when cruising, i.e. “rumm – blatter – blatter”.
Well,I guess its like the compression brakes on trucks,no combustion involved,but noisy as all get out,I’m sure some creative person could tune one for more racket.
The boss and ilk,used to be strict Jap bike fans,finally they terminated to Harleys and we were razzing ,the boss a bit about his Harley,he got mad and kept gunning it till it backfired and it rang everyones ears in the shop(what a expletives deleted)
It’s true that the distinctive Harley sound is largely due to the crank timing. I seem to recall reading years ago that Harley corrected the sound (along with the Don-Knots shaking when stopped) in the design of its big bikes and nobody liked it, so they went back to the potato-potato-potato design complete with shaking.
I know you can get a fairly accurate decibel level app for the iPhones. But no matter how accurate it is, I doubt it would be admissible in court with out millions in government testing and certifications.
The difficulty of proving too much noise in court is the reason a lot of places are busting them for illegal emissions equipment tampering instead.
For a trained cop using a calibrated piece of equipment that saves the results proving it isn’t a problem.
An iPhone would not be admissible. It’s uncalibrated and the operator is untrained.
Some HD owners (with carburetors) turn their engine idle speed down to a near stall condition to exhibit or exaggerate the odd fire distinction, this is why you see them nursing the throttle at traffic lights. The fuel injected models idle too fast for the classic sound.