I never heard of "inverting sound waves". How is that done?
Like noise canceling headphones
Electronic signal can be reversed then sent into an amp and speaker.
The idea (which would not have worked ) would require fast signal switching but this is possible. Where the plan fails is that the signal level has to be matched too. Where the listener is located but it has to be matched everywhere, for all locations. This can’t be done. So the city would be paying for something that is technically impossible.