KTM combatting engine noise crackdown with new onboard sensors

A growing number of authorities – both nationally and internationally – are starting to employ noise cameras to catch riders with bikes considered to be too loud.

While that might sound fair enough if it applied only to blatantly illegal exhausts, there are already situations where a completely stock bike, straight from the showroom, might be able to exceed local noise limits without the rider even being aware of it.

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We’ve already seen noise cameras come into use in several European countries and tests conducted in the UK. Austria has been at the forefront of the battle against loud bikes, going as far as restricting certain bikes from specific roads in the Alps, so perhaps it should come as no surprise that Austrian brand KTM appears to be developing a solution to the problem.

While new bikes already need to pass strict noise tests to be type-approved for sale, those tests are done under specific conditions – setting out speed, acceleration rate, gear and the position of the microphones.

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It’s quite possible that perfectly legal bikes can, by accident or design, be recorded at higher noise levels, for instance in different parts of the rev range or when monitored by mics in a different position.

Emerging solution

KTM has recognised the conflict that sets up between motorcyclists and noise-monitoring authorities and look to be working on an intriguing solution that approaches noise limits rather like speed limits – giving riders the tools to monitor their own bike’s sound levels rather than trying to put a tighter outright restriction on the bike’s sound levels.

Most bikes can easily exceed speed limits, and those speed limits vary from place to place, so rather than restricting performance, bikes are given speedometers – so you control whether or not you’re in breach of the rules. As authorities start to approach noise limits more like speed limits, KTM is developing an equivalent gauge for noise: a volume-meter, if you like.

If riders are going to be expected in future to abide by varying noise requirements, it’s the only true solution. We don’t limit bikes’ top speeds to the lowest speed limit they’ll be riding in, so it makes no sense to limit noise to the lowest level either, provided there’s a way for the rider to keep track of it.

Patented approach

KTM’s patent application is for a ‘visual, acoustic or sensory’ notification to the rider when the bike passes a preset noise threshold – most simply a warning light on the dash – or a ‘digital or analogue display’ that gives a real-time representation of the noise level.

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The bike’s volume would be monitored by transducers – microphones, sensors or both – strategically positioned around the engine and exhaust, calibrated to give a readout that’s representative of the noise level that roadside sensors would be able to pick up.

Alternatively, the bike could be programmed with a noise map based on throttle position, speed, revs and load, so even without real-time sensors it would be able to estimate the noise level in any set of circumstances.

Controlling the volume

On seeing a high noise level, the rider would be able to change gear to drop the revs, or slow down, to reduce the volume. KTM also suggests that preset limits could be included, allowing you to select a low-noise mode that that alters the engine mapping – for instance, the maximum throttle opening or revs – to ensure it doesn’t exceed the limit.

At its most advanced, that preset could be switched on based on GPS position data, so if the bike enters a noise-restricted area, ‘stealth mode’ is automatically turned on.

Data driven

Existing speed, throttle position, gear position, acceleration and rpm sensors would also be used, correlating to a ‘noise characteristic map’ based on previous testing and stored on the bike’s computer.

Relaying information

The information is fed back to a control module (numbered 2 on the drawings) that either relays it to an on-dash volume display or activates a low-noise engine map.

Noise counter

The dash display could be a simple warning light or more involved digital or analogue decibel meter. The latter makes sense, like a speedometer, if riding in areas with multiple different noise limits.

GPS activation

A low-volume engine setting would be able to reduce throttle openings and lower the revs to keep within local noise limits. GPS could be used to tell the bike when it’s entering a low-noise area, either changing the threshold for the on-dash warning or activating the quieter engine mode automatically.