Can the sound of your motorcycle save your life? It’s a question that for years has led to intense discussions among motorcyclists. Romanian motorcyclists have the answer.
MotoADN, Romanian motorcyclists’ organization (and member of FEMA), decided to let science answer the question and set up a series of tests to find out how much of the sound coming from a motorcycle actually reaches the driver of a car. The tests were done in co-operation with the Politehnica University of Bucharest, the most important technical university in Romania, and environmental consultancy company Enviro Consult. You can see a video of the tests below this article.
So, can the sound of a motorcycle save your life? To do this, the sound of the exhausts must be audible to the driver in the car. The sound of the motorcycle must be above the level of the background sound in the car, sound generated by the engine, music, conversations and air current when the car is driving over 60km/h.
In order to have an affect, the sound of the motorcycle must attract attention, i.e. it must be loud enough and it must be heard when the motorcycle is far enough away so that the driver of the car can react. We are not used to identifying the level of a sound, so it is important to have some reference elements. The normal noises that we are surrounded by every day are in the volume range 10-60dB (A). We are quite often exposed to sounds up to 90dB (A). Prolonged exposure to more than 90dB (A) is considered to be a dangerous element to the human ear and may be subject to occupational safety. At a rock concert the volume is at 120dB (A) while exposure to sounds over 130dB (A), even for short periods of a few minutes, is a dangerous element that can affect the hearing system.
How did MotoADN perform the tests?
The test consisted of comparing two data sets. One was the sound measured inside the car, generated by the operation of a motorcycle at high speed and the second was the background sound in the car when the music is turned off or when the music is at a medium volume – volume that allows conversations with passengers without problems. To simulate real situations, MotoADN measured the sound in the car when the motorcycle is 15 meters and 10 meters behind it, but also when the motorcycle was in the driver’s blind spot or when the motorcycle was in front of the car. MotoADN also analysed the distribution of the sound emitted by the motorcycle in front and in the back at various speeds, to measure the influence of speed on noise and how it is distributed in front and behind the motorcycle.
How is the motorcycle heard?
The sound of the motorcycle measured in front of it is 5dB (A) lower than the sound measured behind the motorcycle. In the case of motorcycles with a very quiet exhaust, the engine sounds louder than the exhaust, so the sound measured in front is louder than that measured in the back. More than 15 meters away, none of the motorcycles in the test are heard in the car – even if the noisiest motorcycle in the test produced over 110dB (A). More than 10 meters away from the car, some motorcycles may be heard. But the sound is poorly noticeable with a small difference in volume from the background sound in the car. The sound is also heard in a low frequency zone – 200-400Hz, an area where the human ear has difficulty locating the sound source.
‘The sound produced by a motorcycle is not heard by the drivers of the cars in front of you’
- A motorcycle cannot be heard in the car (in motion) if it is at a distance of more than 15 meters, no matter how modified the exhaust is and no matter the background noise in the passenger compartment.
- At distances of 10 meters from the car, a motorcycle (with a noise level produced above the legal limits) can be heard, but the sound is in a low frequency area where the sound is difficult to identify by the human ear and is difficult to position in space-bar.
- When the motorcycle is near the car or in front of the car, the noises produced will be heard in the car at a level that attracts the driver’s attention, even when the music is at a medium level. At this distance, however, no driver`s manoeuvre that would endanger the motorcyclist could be prevented.
- To be heard in a car 15 meters away, a motorcycle should produce a sound level at the exhaust pipe of more than 135dB (A), a condition that is impossible to accomplish in reality.
MotoADN’s conclusion: loud pipes save lives is a false statement. The sound produced by a motorcycle is not heard by the drivers of the cars in front of you or is heard too late to be able to influence the driver’s decision. Our best advice? Let’s be seen, not heard.
This article is subject to FEMA’s copyright
Photographs courtesy of MotoADN
For the full test report (in Romanian), click here.
Watch the English video of the tests below. For the video in Romanian, click here.