Ask LH: Are Exhaust Noise Rules Different For Cars And Motorcycles?

Ask LH: Are Exhaust Noise Rules Different For Cars And Motorcycles?
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Hey Lifehacker. I often see Harley motorcyles riding by with really loud exhausts and not getting pulled over. But I frequently see people in hotted-up cars that are much quieter getting fined for having a loud exhaust. Are the laws regarding exhaust noise levels different for cars and motorcycles? Thanks, Two Wheels

Bike exhaust picture from Shutterstock

Dear TW,

They are indeed. The laws surrounding exhaust noise are covered by Australia’s Motor Vehicle Standards Act. This defines the limits on the external decibel level of vehicles in order to reduce noise pollution in the community.

The rules and regulations are divided into separate categories depending on the size of the vehicle. For example, passenger vehicles including cars fall inside “Category M”, while two and three wheeled vehicles are classed under “Category L”. There are various sub-classes in each category and the maximum exhaust noise is different for each.

All manufacturers must demonstrate that their vehicles meet a specified noise limit during testing before they can be sold on the market. In other words, it’s a problem that only arises with poorly maintained engines or heavily modified vehicles.

A degree of tolerance is usually permitted for vehicles that fall outside their category’s noise limit, although the amount varies depending on the jurisdiction. Police discretion also plays a pretty large part.

In recent years, the maximum allowable drive-by noise was significantly reduced across all vehicle categories. You can see the current restrictions in the below table:

As you can see, the noise limit is considerably lower for M-Category vehicles than L-Category vehicles. This may explain why you’ve seen modified cars pulled over by police while noisier motorcycles continue to scream by unmolested. If you want to be obnoxiously loud, bag yourself a chopper — The Man won’t be able to touch you (although the pavement might).


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  • At the risk of soundling like a wowser, I’d be really interested in knowing the justifications for allowing motorbikes to be so much louder.

    My guess is that it is assumed that a car, with a fully enclosed engine, is able to employ greater sound deadening features, while a motorbike, with an engine basically sitting in the open, can’t do the same.

    Yet a motorbike engine is smaller, and Harleys (in particular) seem to make it a feature that they are obnoxiously loud.

    Anytime one of those bikes roars past, it kills any conversation, and is almost painful on the ears. Maybe it’s time the laws were revisited?

    • At the risk of soundling like a wowser, I’d be really interested in knowing the justifications for allowing motorbikes to be so much louder.
      More space for more mufflers.
      Cars typically have more than one muffler to reduce the noises coming from the engine – exhaust piping and mufflers often zig-zag under the car, utilising all of that space that bikes dont have.
      My car has 3 mufflers, front, mid, and rear. My bike only has one.

    • My motor cycle has an engine on par and larger than some small vehicles, also given the length of the exhaust you can put on a motorcycle back in the day it was harder to reduce the noise as much as a car, using a single muffer, than it was on a car with usually twin mufflers. Some police also let it slide, because the old saying “if you cant see me at least you can hear me” is true.

      And I think your problem mostly with the noise is from modified exhausts, current and previous generation bikes, with standard exhausts aren’t really noticeably louder than a car, the exahaust note is different which can lead to perception of it being louder. My bike sounds louder than my car sitting and idling in the driveway, but my car is louder.

      oh and it’s at 3/4 rpm, so bikes like mine with a variable exhaust do open up to virtually straight through at a set rpm range.

      • As a biker, I agree that there are lots of unnecessarily loud bikes out there, not exclusively Harleys but they seem to be the obvious stereotype. I also call out (like @dragick) that gives me the s**ts that all us other bikers get lumped into that category. And, sorry, I don’t agree that a loud bike is necessarily safer; I might even suggest that the distraction caused by “what the **** is that noise?!” makes accidents slightly more likely.
        Very happy riding my (no louder than a car) BMW R1200.

    • This topic has been a head-scratcher of mine for years – it seems that every bikie out there is operating a tool for the purpose of producing noise and this should be a perfectly reasonable justification for taking them off the road.

      I can’t count the number of times I’ve been woken by an implausibly-loud motorbike that you can hear coming and going from kilometres away or the hoons whose explosive-fart exhausts define their very being.

      One can only wonder how such vehicles get around on a regular basis when they exhibit such conspicuous and measurable defects.

      • Same here.. I live on a major road, and while the general traffic noise is something that I’ve gotten used to over the years, every time a damn Harley goes past and I either have to pause whatever I’m watching on tv until it’s gone, or try and go back to sleep, I’ve always wondered how in the hell they get away with being so loud when they clearly don’t have to be (other bikes aren’t), and seem to be specifically manufactured to be as loud and obnoxious as possible with complete disregard for every single person living within 1 km radius of a road that they’re traveling on.

        • Actually they’re specifically manufactured to sound like a singer sewing machine. Those exhausts are aftermarket, but significantly increase the power, torque and drivability.

          • Those exhausts are aftermarket, but significantly increase the power, torque and drivability.

            At the expense of everyone else …

      • “seems that every bikie out there”
        Please don’t group us all together like that. The majority of us don’t want stupidly loud noises while riding.

    • Harley’s are the only thing on the road that I find obnoxiously loud. Those and trucks that are deafening (also some buses). They don’t even have a pleasing sound, they are just purely obnoxiously loud to draw attention.

      A classic example would be the south park episode on Harley Riders. This is 90% of them pure and simple. Where a sports bike sounds nice, racey, has a nice note, some V8’s have a nice tune and imports (V6 turbo’s etc) all have a unique sound, Harley’s give all that up to just be the loudest without any pleasing note and just painful to hear (seriously does damage to the ears when going past even when I’m in my house) which is just ridiculous.

  • Exhausts can’t be any louder than bogans cruising around and forcing everyone in a 1 km radius to listen to their fully sick subwoofer maaate!

    If a passenger car louder than 74dB is supposed to draw the ire of the police, there must be a lot of deaf police around.

    • 74db, per exhaust at 3/4 max rpm.

      so with ya fully sik cammed v8 that revs too 8000rpm instead of 6000, though still tested at the original rpm range, coming out your ful sik duel dump tips, you can legally be louder.

    • You’d probably be surprised at just how loud the limits actually are.

      We had a couple girls in the office who used to play their radio while working. Quiet enough that a cubicle over I couldn’t even really tell what was playing, certainly not make out any words.

      But we had a psychopathic bitch who insisted on making trouble for everyone, trying to get herself some stress leave or something, who lodged a formal complaint about OHS, and the noise level.

      And of course, because you have to treat complaints seriously, they sent someone out from OHS with a tool for measuring the volume to see if it violated standards or posed any kind of health risk. She did her measuring, and nope… WELL within limits.

      And then, bringing the complainer over, she said, “I want you to hear how loud this can be and remain within acceptable limits.”

      She cranked the knob all the way to the max, people could hear it everywhere in the building (like… construction site levels) and the OHS lady pointed at the device and said, “Still nowhere near the max. It could get a LOT louder and still be fine.”

      Queen bitch just spluttered about it being ridiculous and ‘something should be done’, etc, etc.

  • Not sure why you’re attacking @zak, i completely agree with him.

    I had an early 90’s V8 with just a mild exhaust to help the car breath better ( yes it was heavily modified ) it idled at 96dB, that was with 2 mufflers and a hot dog.

    I had the police look at it as well as the inspection centre and they said that it was fine due to the amount of power the car had.

  • Nobody would ride a Harley if it weren’t for the obnoxious noise they make. The South Park episode is 100% spot on and covers ALL Harley riders.

  • While I agree some bikes makes tend to be obnoxiously loud (looking at you Mr. Davidson) I feel there is a safety aspect involved for the rider. A scary number of motorists don’t seem acknowledge a motorbike on the road and defensive riding (assume they can’t see/hear you and keep out of blind spots) is a must. A louder exhaust will increase the chances of other motorists being aware of your presence.

  • There’s a bloke in our apartment block that takes off on his Harley every morning at 6am. It used to be 5, but somebody complained that he was waking the entire apartment complex with the obscenely loud engine (possibly the whole neighbourhood), so now he waits until 6 on the dot to be outside of the designated “quiet hours”.

  • I’ve heard along the grape vine that the reason Harley’s are allowed to be so much louder is because they have a patented exhaust system. With the noise being a key part of the design.

    This means that attempts by government to regulate the noise produced breaches trade agreements we have with the US because it’s an infringement on the rights of the company to profit from their intellectual property.

    • That’s kind of hilarious.

      Though when I took my old bomb and its rusted-to-hell muffler to a mechanic, he laughed and said, “Oh, I dunno… there’s a lot of kids pay good money to get a sound like that.”

  • Loud pipes can save lives. We (riders) are often not seen so being heard is an advantage for the rider.

  • Does anyone have a DISTANCE measurement of these ADR noise levels?

    Noise drops off significantly by distance, it drops 3db every 1,000 cm. So where are these ADR numbers being measured at?

    My porch is 10m away as a minimum from the residential street along the front and side of my house. Is 95dB measured at my porch acceptable? If you use the drop-off value of noise over distance it must be over 200db at the exhaust of that motor bike!

    For those more scientifically inclined and not just working on hearsay, this is with a dB meter set to C weighting and the Fast scale. These settings, too, are important as to how noise ratings are calculated.

    It’s extremely unnerving and upsetting. A very loud bang. 3 times in succession (I live in a corner where the vehicle has to take a right turn, then a left and accelerates past my corner lot). Several times a day. At random.

    Surely it’s wrong to say this is Okay.

    This is no laughing matter everyone, please.

    Is my only recourse to sell my house at a loss and move??

    • Hey skris88, I think you must live in my area, I too am driven to distraction by the noise from motorbikes in my street. I have a tattoo shop owner/Harley driver half a block away, and I live between his place and the local bikie’s pub. He is an extremely popular guy 24/7. I have rang the local boys in blue but they’re not interested. Drives me bloody Yarra.

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