Why California's Musical Road Sounds Terrible

California's Musical Road

In 2008, the city of Lancaster, California built its first musical road. Lancaster is about a 1-hour drive north of downtown LA. The town selected the finale from the William Tell Overture, best known as the theme music from the old Lone Ranger TV program. That was an unfortunate choice of song, since the faster you drive, the better it sounds.

What Went Wrong?

Sadly, this road was not done correctly. The grooves in the road were cut at the wrong length making William Tell Overture seem out of tune, but still having the correct rhythm. Every time the wheel hits a groove, it creates a little vibration. Where the grooves are spaced far apart, then these impulse are created one after the other at a slow rate and a low frequency note is created. When the grooves are close together the frequency of the note is higher because the impulses are created one after another more quickly.

Frequency produced by road vs by frequency required by tune

The above graph shows the frequency of road when driven on compared to the correct frequency needed for the tune as designed in the original road construction plans. If the musical road was in tune, all the blue diamonds would lie on the red line. As you can see, they do not line up whatsoever.

Above shows the error that was made cutting the asphalt vs. the correct plans that were originally drawn up.

As Scott explains, it's a relatively simple matter to calculate how far apart to build the road grooves to generate the note you want. The mistake by the road crew was not accounting for the width of the grooves themselves.

Sources:
http://davidsd.org/2008/12/honda-needs-a-tune-up/
https://www.youtube.com/watch?time_continue=2&v=Ef93WmlEho0

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