In both cases, it was mistuned  because of a miscommunication about whether the dimensions for the spacing of rumble strip grooves included the width of the groove itself.
For example, they did a venture with a contractor using a new paving technique, in an attempt to lower future costs for street paving. When it didn't work, there was a clause protecting the city and the work was repaired at no / little cost. Of course the local newspaper raked the city over the coals for the burden of long construction times, completely ignoring that local government had attempted to do something innovative and cost-saving for its citizens.
In another case, the downtown area had become destitute, especially as the main shopping area shifted to the outskirts of town. In an effort to revitalize, the city put up new decorative lamp posts, flower baskets, and did an attractive concrete stamping on new sidewalks. Once again, everybody complained about government waste, when really the city was trying to do what it could to make it a more attractive community and encourage more businesses to reopen / stay downtown.
My point is, while perhaps the singing road didn't have its desired outcome, I give them credit for trying to do something novel.
Having grown up in an area with no sense of style or flourish, I can appreciate the sentiment behind that. Every time I go to Japan or most of the west coast I'm blown away by how much effort goes into making the community look...nice.
However, all too often, a city's attempt to do this involves a contractor or supplier charging obscene amounts of money for the end result. Hence the accusations of waste.
Case in point: Sandy Springs, GA recently paid $99,333 for the city's new logo. The result is the caliber of work I'd expect from a Fiverr task.
Often, what constitutes "waste" is really a matter of spin. During that time, the city was chastised as "anti-growth." Well, guess what, that's because a group of land developers wanted to build thousands of houses, but didn't want to set aside land for schools, fire departments, and other amenities that all the people living in those houses would need. Point being, you can't please all the people all of the time.
Ostensibly, the musical effect was a secondary objective; the primary purpose of this experiment was to test the durability of the specific type of rumble strips used¹.
Obviously you wouldn't be able to get it spot on because of speed vs engine RPM but you could at least tune it for the popular combinations.
So while it may help in isolated cases it is going to amplify the noise for the remainder.
This is exactly the kind of poorly thought out, money wasting boondoggle projects you get when government is a gravy train not held accountable by it's source of funding.
Right now my hometown is engaged in all manner of hand wringing over a pet cemetery. They also put in more bike trail where a rail line was and spent millions of dollars tearing down rail bridge and building a more visually pleasing bike bridge. They must be expecting some fat cyclists since apparently just converting the rail bridge wasn't appropriate. The police are thoroughly overpaid and overstaffed and all run side businesses on taxpayer time.
It sucks that you have to under-fund and under-staff local government and services in order to get them to be well behaved (which to me means do their jobs without screwing around and wasting too many resources on non-mission critical crap) but I guess that's just how it is. If you just keep naively feeding the monster (e.g. "oh, you've squandered all your money on new cop cars and your building is falling down, well we'll give you the money this time but please pinky promise you don't do this again") it will grow big enough that you can't control it.
Edit: I know my last paragraph won't be popular here because it conflicts greatly with the politics of the typical HN reader but I'd appreciate it if you'd actually try and refute something I said.
The source of the noise at any given moment is where the tire is (or has just caused) the strip to vibrate. That point is moving away from the observer about as fast as the car is moving away from the observer
So, the doppler effect is present since the point of friction is moving to a different point on the road, even if the road is stationary.
I'll add one thing: normally you hear Doppler effect with a nearly constant sound (emergency sirens.) Here the pitches are changing, but because our minds instantly recognize the 8-step Western scale we can pick out the frequency shift even though the frequency changes between the different notes may be the larger change.
If it is the tire that makes the noise, it is no surprise that there is a Doppler shift.
In theory you could create the same effect by setting off fireworks.
Unless you're slipping, the point of contact between the tire and the road is always standing still with respect to you
Relativity. Christian Doppler's equation for the change in frequency of a wave, for subsonic velocities, is approximated by three variables: the velocity of the receiver relative to the source, the velocity of waves in the medium and the emitted frequency . The first term is symmetric between a source approaching the receiver and a receiver approaching a source.
(The actual equation measures the velocity of the source and the receiver relative to the medium. Here, too, the symmetry between a source moving towards a receiver, the latter un-moving relative to the medium, and a receiver moving towards a source, the latter un-moving relative to the medium, is preserved.)
Give them too much money and they will build you a singing road.
I can think in some serious and real uses for this. Police surveillance. Helping to solve a kidnapping trough a phone call even if is a hacked one-use phone card. Finding quickly the position of a car accident...
The problem is the noise. If they can find a way to mute the signal and deal with the excessive noise problem could be a rule-changer.
The own asphalt singing in morse trought a hidden microphone the Kilometric point of the road in an infrasound sequence. Somebody could easily find the route or position of a car in a recording or phone conversation just listening to the watermark placed as a invisible soundscape. Is terrific.
IDK, gps seems a much better fit for those. Well, unless you're stupid enough to record a ransom video within earshot of a singing road I guess...
I, for one, would much prefer silent roads. For a while the chirper thing for the crosswalks a block over was turned up way too loud and I had to listen to it all night when I had the windows open because the weather was nice -- even more annoying than a low-battery smoke detector.
On the other hand GPS relies in some signal output that maybe could be discovered by a listening device. This could be just passively recorded by a hidden sort of quiescent black-box device (to be recovered later).
They could’ve perform such an experiment without playing games. Then, they wouldn’t have wasted citizens’ $90,000.