Unnecessary Noise

I was up in New York for a book event yesterday and walking through the neighborhood adjacent to Washington Square, I saw a sign that read "Unnecessary Noise Prohibited." You can't have a sign like that near a philosopher and not expect to be asked what it means for noise to be necessary. When philosophers use the term necessary, it is in contrast to that which is contingent. Surely, they don't mean to disallow any sound which is not physically or logically predetermined or is noisy in all possible worlds. I could choose not to walk there, so the soft plodding of my footsteps there are unnecessary, but surely that's not what they mean.

The use of necessary here seems to mean something along the lines of justifiable. Noise is necessary when you have a good reason for making. But now we've taken one word we don't know the meaning of and replaced it with a phrase that is stunningly vague. What would count as a good reason? Good for the community? That would seem reasonable given that it is a rule of the community. But we could imagine personal emergencies that would count if they were dire enough. How would you draw that line? Given that tickets could be given and fines assessed for the necessity or non-necessity of a given noise, what conditions would be reasonable for determining when a noise would be unnecessary?