We all know by now that Harley-Davidson motorcycles are known for their potato-potato-potato sound. You can recognize a Harley miles away just from its sound (and probably the loud pipes). The same goes for most BMW and Ducati motorcycles.
But did you know that the sounds are engineered? It used to be that engineers and designers looked after the engine and then the motorcycle frame; the sound came automatically afterward. The only thing the engineers looked at when it came to the sound of the engine, was if it stayed within the legal regulations envelope.
If the sound sounded dull, they adapted the exhaust noise. But Harley wanted more. They continued their research and found that people liked the potato-potato-potato sound, so they set out to replicate it on all their motorcycles. During the ’90s they even went so far as to patent their sound, but despite popular believe, their attempt was unsuccessful.
This brought in a new profession in the motorcycle industry; Acoustic Engineers. Almost all, if not all, manufacturers have at least one. Their job is to ensure that when you fire up your engine, it doesn’t sound like a lame duck with a severe flu. Nothing turns off a biker more than the sound of a lawnmower, not a real motorcycle when starting up their bike.
BMW have a special wind tunnel that generates a wind flow of 200 kph, but is totally silent. This allows their engineers to measure and analyze the sound coming from the motorcycle’s engine, exhaust and frame. Special care is taken with vibrations from different parts of the motorcycle, as to ensure that they do not disrupt the bike’s melody. A test dummy sits on top of the motorcycle, and hears everything a normal biker will. That sound is recorded, and analyzed for further improvements.
The motorcycle sound is made out of three different parts; the air intake, the engine noise and the exhaust, but other parts of the motorcycle can negatively influence the engineered sound, like a dry clutch. So next time your ride your bike, enjoying the throb and sound of your engine (especially in a tunnel), remember that the sound was made, not an accident.
Of course all this goes away with the coming of the electric motorcycle, unless you use a CD player with the desired sound.