PART 1 : Reduce Noise in Your Custom Motorcycle - The Regulations 1

PART 1 : Reduce Noise in Your Custom Motorcycle – The Regulations

Introduction to Motorcycle Noise Regulations

It’s 8am on a crisp Sunday morning. You’ve decided to get up a bit earlier to get a head start on what is looking like a promising day of riding. It’s a picturesque blue-bird day. If you’re in Melbourne like I am, autumn and spring provide some of the best riding weather. This means you’re ready to go for a quick scoot around town, up to the ranges or just for a coffee to show off your newly built custom machine.

You’re in the garage now, your roller door is open and you’ve got lights…ignition… lift-off!

Your garage, which acts as a directional sound propagating chamber only intensifies the noise coming from your open and unrestricted exhaust. With that, you’re on-course to waking up half your neighbourhood, and especially those directly in line of the open garage.

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Don’t get me wrong. I love the noise of a cool loud custom. But there are times when they’re just plain too loud. The noise coming from an un-muffled/ under-muffled exhaust can be irritating at best, let alone all the negative attention it delivers. So the solution is to muffle the exhaust, and let the paintwork and custom gear become the loud part of the bike.

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Why is it important to consider noise? Three reasons:

1. Regulations (PART 1)

2. Performance (PART 2)

3. Appeal (PART 2)

I’ll tackle each of these in the sections below before taking you through our process of modifying an existing/custom exhaust. You’re welcome to skip through the sections not applicable to where you’re from.

Vehicle noise regulations around the world:

Australian Motorcycle Noise Regulations

New vehicles are governed by the Federal Department of Transport (DITRDC – The acronym changes every few years to include or remove something new. Bureaucracy at its finest). This means that new vehicles need to meet the performance and technical standards set out in the 3rd Edition Australian Design Rules (1989 and onward). The design rules have applicability criteria for certain years of production. This means that new design rules can come into effect for new vehicles in the future. Australia harmonises the majority of its rules, including Noise (ADR 83/00) with UN Regulations.

However, a used vehicle is not governed by the federal sphere after its first day of road-use. This is often the day of registration. In-service vehicles are then governed under the state that they are registered in. In general this means that the motorbike must meet the following:

  1. Continue meeting the ADRs applicable to its day of manufacture. (3rd Edition ADRs for vehicles manufactured after 1989, and 2nd Edition ADRs for vehicles manufactured before 1989).
  2. The registering States Road Safety (Vehicle) Regulations.
  3. Modification Guidelines and National Codes of practice – VSB 14 Section LL   

When it comes to noise, Engineering Assessors will most likely not conduct a full ADR equivalent drive-by test of the build. It’s time consuming, expensive and often not necessary. For reference however, a motorcycle with more than 175cc engine must not emit more than 80 dB(A) during a drive-by test which is taken at 7.5m from the line of travel. Note that this is a wide open throttle test.

A stationary noise test will most likely be done by the Engineering Assessor (where a modification certificate is required to register a modified bike) and by the Road Worthy Assessor. As a guideline the following stationary noise limits need to be met:

Built February 1985 and onward: 94 dB(A)

Built before February 1985: 100 dB(A)

Note that this test is done at 50% RPM, 45 degrees to the normal at end of the exhaust and 500mm away at a height of no less than 200mm from the ground.

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It’s also important to note here that modifications such as those to noise technically require an engineering approval by an AVE (Accredited Vehicle Examiner). Each state has their own scheme but they generally follow similar principles – when it comes to noise, it’s those outlined above. 

USA Motorcycle Noise Regulations

Similarly, the USA have their own version of Rules and Standards that new vehicles must adhere to before they are accepted in the marketplace. They differ considerably when compared to the UN Regulations and focus primarily on 3 areas; 1 crash avoidance, 2. Crashworthiness, and 3 post-crash survivability. Therefore, things like noise and emissions fall under state requirements and the local EPA, and are not covered by the federal sphere.

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In Summary, all motorbikes need to be equipped with a good functioning muffler that prevents excessive or unusual noise and annoying smoke. Depending on the state that you’re in this can be somewhat open to interpretation. In states like Arkansas and Illinois this means a factory-installed muffler or one duplicating factory specifications. i.e. no aftermarket mufflers that increase the noise of the original muffler.

The state of California has the same requirement as above, but goes a step further and clarifies what this means for new or factory installed specifications. In the Californian Vehicle Code 27151 Article 2.5 new vehicles must meet the following noise requirements depending on their year of manufacture. 

            Before 1970: 92 dB(A)

            After 1969 and before 1973: 88 dB(A)

            After 1972 and before 1975: 86 dB(A)

            After 1974 and before 1986: 83 dB(A)

            After 1985: 80 dB(A)

This is measured during a drive-by test at 15 metres (50 feet) from the centreline of travel. For reference, the Australian ADRs and UN Regulations do this test at a distance of 7.5 metres (25 feet). Therefore, the stationary noise limit of 94dB(A) shown above can be used as a guideline for those in the US. That is, meet this stationary requirement and you likely pass the Californian drive-by test with flying colours.  

We can’t cover it all here but for more detailed information on your state you can go to:

European Motorcycle Noise Regulations

If you’re from Europe you’ll be well accustomed to the UN model regulations for motor vehicles. When it comes to new motorbikes and noise levels, we refer to UN Regulation No. 41 (Uniform Provisions Concerning the Approval of Motor Cycles with Regard to Noise). There are also EU directives but we won’t go into specifics here because they typically apply to specific countries.

It doesn’t stop there though, there’s another Regulation and that is UN Regulation No. 92, which is specific to aftermarket mufflers.

What does all this mean for in-service vehicles? Well, it also depends on the country.

Let’s take Germany as an example – it’s known for its amazing performance engineering, its Autobahn and of course it’s stringent rules. If you’re making a café racer, a scrambler or any other custom your best bet is to consult your local test and homologation houses like Dekra or TUV. In fact, in Germany it’s likely that getting your ride insured without their approval is unlikely.

Noise level of every vehicle is registered. If the exhaust modification increases the noise from its original level, it needs permission. This means that if the Polizei pull you over and you don’t have permission, you’ll be receiving a ticket, as well as an in-depth look over for any other non-compliance. The noise levels that must not be exceeded follow the same principle as most states in the USA and are captured in UN Regulation 92. That is, the new muffler should not be increasing the noise levels as per Regulation 41 (New vehicles). Here are the noise limits:

  1. Category 1 (PMR* < 25) = 73 dB(A).
  2. Category 2 (25 < PMR < 50) = 74 dB(A).
  3. Category 3 (PMR > 50) = 77dB(A).

*Where PMR = Power to mass ratio index can be calculated using the following formula = PMR= (kW/ (mkerb+ 75))* 1000

Importantly, this is measured during a drive-by test (This is where the Australians get it from). A diagram of the drive-by test can be seen below.

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Now you may wonder, what this means for your 1970’s CB750? Well you’d need to dig up the limits that cover that period of manufacture. I once again refer to the stationary noise limits used in Australia. If you’re stationary noise level is under 94dBA, you’ll be in the right ball-park for passing.

That’s it for a summary on the regulatory side of things. If you’re interested in the performance aspects and building a custom muffler insert then tune into Part 2!

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