This is done so that noise concerns can be understood not only in terms of volume, but in terms of pitch. Once a walk down a public street is viewed as an incidental melody and properly labelled, better strolling and planning can take place.
For example, if a person walks down a street and hears air conditioners and construction equipment forming the melodic fragment A, G, F, then it is natural to want to hear an E after that. This might influence where you go in the city. It would also make sense to tune the machines in your business to sound like an E to attract people your way. Similarly, you may wish to create extremely dissonant harmonies to keep people away.