In another thread, MRieck asked me what I felt were acceptable motorcycle exhaust noise limits, and wanted number to quantify. So, I took some time to do some research. Here's my response/report.
You want my standards, government standards, or AMA's standards? (AMA = American Motorcycle Association.) Mine are simple, if it is louder than a stock exhaust system, it almost certainly is too loud, particularly if it has no DOT approval. But, my major personal concern is in how my home is invaded by drive by sound terrorists. (More about this later.) But, loud exhausts are an offense against society and a disservice to ALL motorcycle riders, imo.
AMA has guidelines, here:
How to Perform a SAE J2825 Motorcycle Sound TestData gathering:
OSHA reports that SPLs above 85db leads to risks of Tinnitus and hearing loss. (I am an example of that btw, as I have experienced that and far higher levels as well). Above 85db, you are advised to use hearing protection. Will the users of loud pipes supply hearing protection to all those that are in near field vicinity of the louder motorcycle? (Seems unlikely)
AMA tests for 92db at idle and either 100db for 3 and 4 cyl bikes, a 96db for all others including twins. My personal opinion is that this is still too loud and certainly unnecessary. The Feds version is actually more liberal, despite the lower number published. "By state regulation, motorcycles manufactured in or after 1979 cannot exceed a noise level of 84 decibels (dB) when traveling more than 35 mph on a paved street or highway."
They do, however, measure it differently than the AMA. "The noise level must be measured 50 feet from the centerline of the vehicle", Feds say.
See: j331a,
http://www.google.com/url?sa=t&rct=j&q=j331a&source=web&cd=1&ved=0CEwQFjAA&url=http%3A%2F%2Fwww.temple.edu%2Flaw%2Ftjstel%2F2006%2Fspring%2Fv25no1-Torrey-and-McCulley.pdf&ei=L14HUIyhJoWL2AW76MjMBA&usg=AFQjCNHaLttD86IP-YKUO3rO51WZqN9B_A&cad=rjaCurrently, federal law reports the maximum noise emissions for motorcycle exhaust systems as 84-86 dBA. (Still @ 50 Ft)
For more detail see : 40 C.F.R. § 205.166
These would be 50 ft measurements. I assume the EPA/Gov expects that if you can stay 50 ft or more away from a motorcycle your hearing should not be damaged.
Sound reading measurements diminish 6dB for every doubling of distance. So, working backwards, 84DB at 50 ft from source will be 90 DB at 25 Ft, 96 db at 12.5 ft, 102 db at 6.25 ft, 108 at 3.125 ft etc. See first graphic below. It shows how much to subtract from the source level in DB, with distance. For example, a 60 DB noise source will not be noticed 1000 ft away from the source.
AMA's suggested standard is actually more restrictive than current Fed requirements. I prefer AMA's standard. And, I expect the noise tolerance will become more restrictive in the future.
For this analysis, I'll take a 2 level of concern approach to noise. The first being actual damage to the human ear. If you care about your own hearing the second graphic summarizes the personal risk, as well as risks to bystanders. ( As I admitted earlier, I didn't know about these risks earlier in life, as I still believed I was invulnerable, and now have the resulting damage to prove it wasn't so.) Anyway, graphic 2 outlines the risks that your machine impresses to those in the vicinity.
If you personally like it loud, now you know what risks you are taking. If you like it loud for others, you can now see how you may be harming others with careless behavior. If your machine emits more than 115 db, it only takes brief exposure to begin hearing damage. But, it certainly matters how far away your machine is from the ear-to-be-damaged.
The second level of concern is the individual annoyance factor which varies with either waking or sleeping. An alarm clock or telephone ring are designed to wake humans and draw their attention at 60-66db. Noises this loud are intended to startle. Are you happy to wake up random people with your motorcycle during a drive by? An AMA 100dBA motorcycle only needs to be 80 ft away to be equivalent to an alarm clock. To keep from interfering with normal speech you'd need to be 150 ft. from their living room. Graphics 3&4 show how people perceive noise sources a equate their annoyance factor. I also found some graphics (5 and 6) which were published by local government bodies depicting acceptable noise intrusion levels.
Graphics 7 & 8 show what happens in communities where noise such as loud pipes, have been collectively deemed a nuisance. Having a loud exhaust means that there are places where you may not operate your machine and limit you access due to intrusive and disturbing machine configuration.
Graphic 9 is a precursor to what can happen when ALL motorcyclist are painted with the same characteristic brush. You may claim they over reacted. But, it is not difficult to imagine what the stimulus was that prompted making a sign to that effect.
I found myself strangely attracted to the device in graphic 10, and felt that just maybe there was something there that was worth adding to my tool collection.
I expect some may proclaim that our bikes were made before 1979 and therefore fall into a loophole of non-required compliance. Technically, I agree to that legal aspect for FED and EPA.. However, that doesn't mean the states and localities can't take a more comprehensive approach to all two wheeled vehicles, especially those that are blatant offenders. Certainly nothing will prevent them from issuing citations, if only for reverse harassment of the noise offender. Almost all communities have a noise ordinances, and many have time of day/night restriction clauses. These laws didn't get created because everyone kept quiet, out of consideration for others.
Some parting thoughts...
If you go out of your way to be discourteous to others do you still demand courtesy from others?
Or the reverse, if someone is discourteous to you, do you respond with courtesy.
If 12 loud bikes drive by a non-rider in a car or truck in traffic, do you think said driver is more or less likely to cut off the next bike they notice approaching? (Can always use the I didn't see you/hear you explanation.) The basic psychology is that one normally wishes to eliminate intrusions into their life, either in a conscious or subconscious way.
A human scream is about 80 db. This has been used to evoke a fight or flight response since the dawn of man. Humans are pre-conditioned to respond in this way to these sound levels.
Do you want to reach into peoples homes to evoke a fight or flight response each time you drive by? Are you actually inviting a fight?
You could say that humans weren't designed to interact with other humans with SPL's above 80-90db and natural phenomena only exceed these levels on very rare occasion.
After doing the research and thinking about it more, I don't really see why motorcycle are allowed, or need, to be louder than autos, actually.
If you operate you vehicle in a residential area and have any expectation to NOT annoy the residents, you should keep their exposure down below 70 db (60db preferred) at the destination.
For a 100db motorcycle that means stay at least 50 and preferrably 100 feet away.
The real answer is related to where and how much the noise is produced and subsequently delivered. If all homes were universally 300 ft away from any roadway your AMA compliant bike could travel any where without annoyance apart from marching the rider and passenger toward tinnitus and deafness. I expect, though that most expect to drive their bikes wherever there is a road and ignore any possible impact on residents within 50 ft (or 25 ft). If so, you should have the responsibility to keep the bike at least as quiet as when it came off the showroom floor.
My front door is 75 ft away from street center, in case you are wondering (I measured).
Cheers,
