David Simmons-Duffin @ Caltech
Honda Needs a Tune-Up Dec 23, 2008
This is the story of how Honda engineers screwed up a big expensive project with a simple arithmetic mistake, tried to fudge their result with sound editing software, and congratulated themselves for being totally awesome.
When I was a kid, my family used to drive up to The Pinery in Ontario, a beautiful park by Lake Huron. Very scenic. My favorite part, though, was a stretch of road a half-hour outside of the park. To discourage reckless Canadians from barreling past the houses and barns, the local government carved five sets of grooves in the road before every stop sign. Drive over them, and the car would vibrate: “vbvbvbvb... vbvbvbvb... vbvbvbvb... vbvbvbvb... vbvbvbvb.” The faster you drive, the higher the pitch.
My Dad is a musicologist, with a particular interest in tuning. So there was no way he was going to pass up the chance to experiment with this instrument. Every time we approached some grooves, he'd start fast over the first set, and try to slow down by the last set, to play a descending scale: G-F-E-D-C. If there was no oncoming traffic after the stop sign, he'd swing over to the other side of the road and play an ascending scale as we sped up.
Ratios of speeds correspond to ratios of vibration frequencies, which correspond to intervals between notes. To play an ascending scale C-D-E-F-G, you need to drive at these ratios to your starting speed: 1 - 9/8 - 5/4 - 4/3 - 3/2 (for example, 24 - 27 - 30 - 32 - 36 mph). 1
Playing a scale with a '95 Toyota Previa is not easy. The notes tend to come out a little wonky — we'd get the half-step between E and F too wide, and with not enough space between F and G. It usually sounded kinda modal... but still awesome.
Professionals?
So imagine my delight when I heard about this musical road [CNET] that Honda built in Lancaster, CA.. A team of engineers carved some grooves into a highway that were carefully spaced to play the William Tell Overture as you drive over them at a constant speed. Awesome, right? The problem is, it's spectacularly out of tune.
Here's the original melody:
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