Actually, Loud Pipes Don’t Save Lives

From Autoweek

Some motorcycle riders love loud pipes. “That’s the sound of freedom, boy!” Others find them as pleasant to hear as a two-stroke leaf blower right outside the window. But the defense of the loud-pipers has always been that, “Loud pipes save lives.” A recent scientific study says no, loud pipes don’t save lives (but it does not address the question of whether loud pipes annoy anybody).

The study was undertaken by the Association for the Development of Motorcycling in Romania, in conjunction with the Department of Road Vehicles at the Polytechnic University of Bucharest together with the Netherlands-based noise emissions specialist Enviro Consult. The idea was to see how much noise from motorcycle exhaust pipes actually reaches the ears of car drivers. It was not possible to replicate the tests while both motorcycle and car were moving, so the tests were done statically on a quiet side street lined with large apartment buildings. There does not appear to be any traffic visible to affect the sounds recorded.

Testers measured the sound heard inside the car with the windows rolled up, the engine running at between 2,500 and 3,000 rpm and the radio playing at 20 decibels, or quiet enough to have a normal conversation without raising your voice. For comparison, the sound in your house right now is probably 40 dB, a vacuum cleaner makes about 75 dB, and a lawn mower is between 80-89 dB.

They used six different motorcycles in the test, all revving at full rpm, and parked at distances of 50 feet behind the car, 33 feet behind, right next to the car, and then right in front of the car. The sound of each of the six motorcycles at redline registered between 80 dBA and 110 dBA.

The result? At 50 feet behind the car, “none of the motorcycles in the test can be heard inside the car.” At 33 feet behind the car, “even the noisiest motorcycles tested can hardly be heard inside the car.” With the motorcycles’ front wheel next to the car’s rear wheel, one of the motorcycles can be heard inside the car and three motorcycles can almost be heard but, “unfortunately it is too late to be safe.” With the bikes 13 feet in front of the car the motorcycles cannot be heard. “Car sound isolation in front is better than sound isolation from the side.”

The conclusion of the study specifically says that the assumption “loud pipes save lives” is false. The driver of the car cannot hear a motorcycle if it is more than 33 feet behind the car, and as it gets closer than 33 feet to the car “even if the car driver hears you, it is too late to react safely. So we consider that noise is not a warning for the car driver. It can even be considered a danger because you will not have time to adapt to the new reaction of the driver.”

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