| Author | Message | ||
     Lovedabueller |
`??? | ||
| Jdugger |
Depends on the specification. Sound pressure levels are generally specified as db at distance. There are different standards, and one of the ways some firms "cheat" is to simply pull the microphone back. Typical audio measurements at made at 1 meter. I'm not sure with vehicles. | ||
| Albert666 |
half a metre at a 45 deg angle, although that can be open to interpretation too, thats uk spec anyway | ||
| Stirz007 |
Jim - Some Firearm supressor manufacturers apparently fudge the set-up, too. Here's a few standards I'm somewhat familiar with, but I am not in the business of testing mufflers - Dean probably knows the skinny on this. ASTM E2202 - 02(2009) Standard Practice for Measurement of Equipment-Generated Continuous Noise for Assessment of Health Hazards - this is a 'base' standard, applicable to vehicles, among other things. It's intended to protect workers against hearing loss, so this standard requires measurement at the operator location for ground vehicles. AASHTO looks at the noise generated for vehicles in motion - usually taken 50 feet off centerline of travel. Interestingly, tire noise for trucks and cars tends to dominate over about 35 mph. SAE J1287: Measurement of Exhaust Sound of Stationary Motorcycles: requires microphone set 0.5 m away from outlet, at same height as outlet, and at a 45 degree angle from centerline on each side of motorcycle having an outlet. http://www.amraracing.com/2009/pdfs/SAE%20J1287.pd f The California standard is (Note DOES NOT apply to motorcycles): "Section 1030-1036, 13 CCR, were intended to be used by Licensed Muffler Certification Stations as a means of detection if an exhaust system met the requirements of the Muffler Certification Program (When those programs were operational) They specify testing procedures for motor vehicle exhaust noise alone (as opposed to total vehicle noise) This procedure specifies a limit of 95 dB measured 20 inches from the exhaust pipe outlet with the engine operating in neutral, typically at speed of 3000-5000 rpm. It applies only to passenger vehicles. It does not apply to motorcycles or to vehicles over 6000 pounds gross weight." http://www.cent-21.com/laws/exhaust-us.htm I'm sure there are EPA and Euro standards not mentioned that are out there, too..... | ||
| Azxb9r |
That depends on how your local noise ordinance reads  | ||
| Buelldyno_guy |
Google both the AFM and AMA rule books, I bet there are some sites that have the sound rules for Europe also. Any of those measuring methouds should be OK for the track and for the street just apply a lower limit. |
